Patent Application
20190034286
The present invention relates to a computer program product, system, and method for asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups.
Data storage systems, particularly at the enterprise level, are usually designed to provide a high level of redundancy to reduce the risk of data loss in the event of failure of a component of the data storage system. Thus, multiple copies of data are frequently stored on multiple systems which may be geographically dispersed. Thus, data from a host to be stored in the data storage system is typically directed to a primary system at a local site and then replicated to secondary system which may be geographically remote system from the primary system.
The process of replicating, that is, copying data over to the secondary system can be setup in either a synchronous or asynchronous relationship between the primary system and the secondary system. In a synchronous relationship, any updates to the primary system are typically synchronized with the secondary system, that is, successfully copied over to the secondary system, before the primary system reports to the host that the data storage input/output operation has been successfully completed. As a result, data storage to a primary storage system and a secondary system in a synchronous relationship may adversely affect system performance of the host while the host awaits completion of the synchronous copy operations. In storage systems in which the primary and secondary systems are widely separated, delays to completion of the synchronous copy operations may be greater, which can further adversely affect host performance. For example, in storage systems in which the primary system and the secondary system are separated by a geographical distance of 300 kilometers (Km) or more, for example, there can be a delay of 3-5 seconds (or more) before the data is successfully replicated at the secondary system.
As a result, storage systems frequently employ an asynchronous relationship between a primary system and a secondary system, particularly if the secondary system is geographically distant from the primary system. In an asynchronous relationship, successful updates to the primary system are typically reported to the host as a successful storage input/output operation without waiting for the update to be replicated to the secondary system. As a result, the host need not wait for the data replication to the secondary system to be completed, and the performance of the host system may be enhanced accordingly.
As the name suggests, in an asynchronous relationship, the primary system and the secondary system may not be fully synchronized at any one time. Thus, data stored on the secondary system typically lags that stored in the primary system. Accordingly, new data stored on a primary system may not be stored on the secondary system for an interval of time such as 3-5 seconds, for example.
In data replication systems, data is typically maintained in volume pairs, comprising a primary volume in a primary storage device and a corresponding secondary volume in a secondary storage device that includes an identical copy of the data maintained in the primary volume. The primary and secondary volumes are identified by a copy relationship in which the data of the primary volume, also referred to as the source volume, is copied to the secondary volume, also referred to as the target volume. Primary and secondary storage controllers may be used to control access to the primary and secondary storage devices.
A near instantaneous copy of a volume may be generated using a point-in-time snap copy function such as the IBM® FlashCopy function, for example. The point-in-time snap copy function creates a “snapshot” of the contents of a source volume as of a particular time in a target volume which may be referred to as the point-in-time snap copy volume. One version of a point-in-time snap copy function transfers the contents of the source volume to the point-in-time snap copy volume in a background copy operation.
A target bitmap having a bit for each track of the point-in-time snap copy volume, is used to indicate tracks which have not yet been transferred to the point-in-time snap copy volume. As the contents of each track of the source volume is copied to the target volume, the corresponding bit of the target bitmap is updated (typically reset) to indicate successful transfer of the contents for the associated track. Any read operations directed to a track of the point-in-time snap copy volume which has not yet received the contents of the corresponding track of the source volume, are redirected to obtain the contents of that track from the source volume. Accordingly, the contents of a point-in-time snap copy volume are immediately available albeit indirectly, before any tracks have actually been transferred to the target volume. Conversely, if the host directs an update to a track of the source volume before the contents of that track have been transferred to the point-in-time snap copy volume, the contents of the track of the source volume are transferred to the point-in-time snap copy volume before the update is permitted to overwrite the contents of that track of the source volume.
Another version of a point-in-time snap copy function omits the background copy operation. Thus, the contents of the source volume are not transferred to the point-in-time snap copy volume in a background copy operation. Accordingly, any read operations directed to a track of the point-in-time snap copy volume are usually redirected to obtain the contents of that track from the source volume. However, if the host directs an update to a track of the source volume, the contents of the track of the source volume are transferred to the point-in-time snap copy volume before the update is permitted to overwrite the contents of that track of the source volume.
In a synchronous data replication system, a point-in-time snap copy volume may be made of a primary volume at the primary system with respect to the contents of the primary volume as of a particular point-in-time, and a point-in-time snap copy volume may be made of a secondary volume at the secondary system with respect to the contents of the secondary volume as of the same point-in-time. Because the primary and secondary volumes are synchronized, the respective point-in-time snap copy volumes will also be synchronized and therefore consistent with each other notwithstanding that the point-in-time snap copy volumes are made in different places, that is, the primary system and the secondary system. In this manner, a pair of snap copies may be formed, one local and one remote, in which the local and remote snap copies are consistent with each other.
To maintain a degree of consistency of data across multiple volumes at a secondary system in an asynchronous data replication system, the IBM® Total Storage disk subsystem Peer-to-Peer Remote Copy (PPRC) function supports the concept of a PPRC consistency group. Volumes in a PPRC relationship that are configured into a PPRC Consistency Group are maintained to ensure that a group of updates made to volumes at the primary system are also eventually made on the volumes at the secondary system to maintain data consistency for those volumes of the group. Accordingly, consistency groups may be formed between volumes of the primary system and the secondary system which are consistent with respect to a particular set of updates or a particular point in time, notwithstanding the overall asynchronous relationship between the primary system and the secondary system.
A local point-in-time snap copy volume maybe made of a primary volume at the primary system with respect to the contents of the primary volume as of a particular point-in-time. Similarly, a remote point-in-time snap copy volume may be made of a secondary volume at the secondary system with respect to the contents of the secondary volume as of a particular point-in-time. However, because the primary and secondary volumes are not synchronized in an asynchronous data replication system, the respective local and remote point-in-time snap copy volumes may not be not be consistent with each other even if the secondary volume is part of a consistency group with respect to the primary volume. For example, a command to establish a pair of local and remote snap copies involving volumes of a consistency group being formed, may not be consistent with respect to each other. Hence, to provide a remote backup copy of a local point-in-time snap copy volume of a primary volume at the primary system, the point-in-time snap copy volume generated at the primary system is typically transferred over a network to the secondary system.
One general aspect of asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups in accordance with the present description, is directed to receiving a local-remote pair point-in-time snap copy establish command to establish a local point-in-time snap copy in a local data storage system, and a remote point-in-time snap copy in a remote data storage system. In one aspect, establishment of the remote point-in-time snap copy relationship may be delayed as a function of the state of a consistency group formation process upon receipt of the local-remote pair point-in-time snap copy establish command. As a result, consistency of the local-remote pair of point-in-time snap copies may be realized, notwithstanding an asynchronous relationship between the local and remote storage systems.
In one embodiment, operations include mirroring data asynchronously from a first data unit stored in a storage unit of a first storage system at a first location, to a second data unit stored in a storage unit of a second storage system at a second location, mirroring data asynchronously from a third data unit stored in a storage unit at the first location, to a fourth data unit stored in a storage unit at the second location, and receiving a command to establish a local-remote pair of point-in-time snap copy relationships including a local point-in-time snap copy relationship in the first storage system, from the first data unit as a snap copy source, to the third data unit as a snap copy target, and including a remote point-in-time snap copy relationship in the second storage system from the second data unit as a snap copy source, to the fourth data unit as a snap copy target.
In one aspect, the operations include, in response to the command initiating a local-remote pair of point-in-time snap copy relationships, determining a state of a consistency group formation process upon receipt of the command wherein a plurality of states includes an idle state and a draining state wherein an idle state exists in which no consistency group which includes the second and fourth data units is actively forming and wherein a draining state exists in which a consistency group which includes the second and fourth data units is actively forming, and delaying establishment of the remote point-in-time snap copy relationship if the state of a consistency group formation process is determined to be in a draining state in which a consistency group which includes the second and fourth data units is actively forming in a draining state upon receipt of the command. In one embodiment, the plurality of states further includes an increment complete state following completion of the draining state, wherein delaying establishment of the remote point-in-time snap copy relationship is terminated if the state of a consistency group formation process is determined to be in an increment complete state following a draining state in which the command was received.
In one aspect, the initiating a local-remote pair of point-in-time snap copy relationships further includes establishing the local point-in-time snap copy relationship independently of the state of a consistency group formation process. Accordingly, in one embodiment, the local point-in-time snap copy relationship may be established without significant delay.
In another aspect, the initiating a local-remote pair of point-in-time snap copy relationships includes reserving resources of the second storage system for subsequent establishment of the remote point-in-time snap copy relationship. In addition, initiating a local-remote pair of point-in-time snap copy relationships further includes establishing the remote point-in-time snap copy relationship using the resources of the second storage system reserved for subsequent establishment of the remote point-in-time snap copy relationship, if the state of a consistency group formation process is determined to be in an increment complete state following a draining state in which the command was received. In another aspect, the initiating a local-remote pair of point-in-time snap copy relationships further includes establishing the remote point-in-time snap copy relationship using the resources of the second storage system reserved for subsequent establishment of the remote point-in-time snap copy relationship, if the state of a consistency group formation process is determined to be in an idle state in which the command was received.
In yet another aspect, initiating a local-remote pair of point-in-time snap copy relationships further includes determining a snap copy sequence number as a function of a consistency group formation process upon receipt of the command, and associating the resource reserving for subsequent establishment of the remote point-in-time snap copy relationship to the determined snap copy sequence number. In addition, the initiating a local-remote pair of point-in-time snap copy relationships further includes associating the remote point-in-time snap copy relationship to the determined snap copy sequence number.
In one embodiment, the first data unit is a first volume and the second data unit is a second volume.
Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. Other features and aspects may be realized, depending upon the particular application.
A system of one or more computers may be configured for asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups in accordance with the present description, by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform operations for asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups. For example, one or more computer programs may be configured to perform asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions.
As previously noted, in an asynchronous data replication system, a point-in-time snap copy volume may be made of a primary volume at the primary system with respect to the contents of the primary volume as of a particular point-in-time. Similarly, a point-in-time snap copy volume may be made of a secondary volume at the secondary system with respect to the contents of the secondary volume as of a particular point-in-time. However, because the primary and secondary volumes are frequently not fully synchronized in an asynchronous mirror relationship, the respective point-in-time snap copy volumes may not be synchronized and therefore may not be consistent with each other. Hence, to provide a backup copy of a point-in-time snap copy volume of a primary volume at the primary system, and to store the backup copy at the secondary system, the point-in-time snap copy volume generated at the primary system previously was transferred over a network to the secondary system.
In accordance with one aspect of the present description, it is recognized that in many applications, most of the data to form a point-in-time snap copy volume at the secondary system already resides on the secondary system due to the asynchronous mirror relationship. Accordingly, asynchronous local and remote generation of consistent first and second point-in-time snap copies in accordance with one embodiment of the present description, can obviate much of the transfer of data over a network in creating consistent first and second point-in-time snap copies located at different sites.
One general aspect of asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups in accordance with the present description, is directed to receiving a local-remote pair point-in-time snap copy establish command to establish a local point-in-time snap copy in a local data storage system, and a remote point-in-time snap copy in a remote data storage system. In one aspect, establishment of the remote point-in-time snap copy relationship may be delayed as a function of the state of a consistency group formation process upon receipt of the local-remote pair point-in-time snap copy establish command. As a result, consistency of the local-remote pair of point-in-time snap copies may be realized, notwithstanding an asynchronous relationship between the local and remote storage systems.
In one embodiment, operations include determining a state of a consistency group formation process upon receipt of a local-remote snap copy pair command as at least one of a plurality of states wherein the plurality of states includes an idle state in which no consistency group which includes units of the command is actively forming, and a draining state in which a consistency group which includes units of the command is actively forming. In one aspect, establishment of the remote point-in-time snap copy relationship of the local-remote pair is not delayed if the state of the consistency group formation process is determined to be in an idle state in which a prior consistency group has been completed.
In a completed consistency group, a volume of the secondary storage will be consistent with respect to a volume of the primary storage. Hence, a remote snap copy of the secondary volume will be consistent with a local snap copy of the primary volume.
Conversely, establishment of the remote point-in-time snap copy relationship of the local-remote pair is delayed if the state of the consistency group formation process is determined to be in a draining state in which a consistency group being formed has not yet been completed. In one embodiment, the plurality of states further includes an increment complete state (also referred to as an idle state) following completion of the draining state, wherein delaying establishment of the remote point-in-time snap copy relationship is terminated if the state of a consistency group formation process is subsequently determined to be in an increment complete state following a draining state in which the command was received. As noted above, in a completed consistency group, a volume of the secondary storage will be consistent with respect to a volume of the primary storage. Hence, a remote snap copy of the secondary volume will be consistent with a local snap copy of the primary volume.
In another aspect, the initiating a local-remote pair of point-in-time snap copy relationships includes reserving resources of the second storage system for subsequent establishment of the remote point-in-time snap copy relationship. In addition, initiating a local-remote pair of point-in-time snap copy relationships further includes establishing the remote point-in-time snap copy relationship using the resources of the second storage system reserved for subsequent establishment of the remote point-in-time snap copy relationship, if the state of a consistency group formation process is determined to be in an increment complete state following a draining state in which the command was received. In another aspect, the initiating a local-remote pair of point-in-time snap copy relationships further includes establishing the remote point-in-time snap copy relationship using the resources of the second storage system reserved for subsequent establishment of the remote point-in-time snap copy relationship, if the state of a consistency group formation process is determined to be in an idle state when the local-remote pair establish command was received.
In one aspect, the initiating a local-local-remote pair of point-in-time snap copy relationships further includes establishing the local point-in-time snap copy relationship independently of the state of a consistency group formation process. Accordingly, a local snap copy relationship may be established without significant delay regardless of the state of a consistency group formation process in some embodiments. Other aspects and advantages may be realized, depending upon the particular application.
A system of one or more computers may be configured for asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups in accordance with the present description, by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform asynchronous local and remote generation of consistent point-in-time snap copies in consistency groups operations. Thus, the operations described herein are performed by logic which is configured to perform the operations either automatically or substantially automatically with little or no system operator intervention, except where indicated as being performed manually. Thus, as used herein, the term “automatic” includes both fully automatic, that is operations performed by one or more hardware or software controlled machines with no human intervention such as user inputs to a graphical user selection interface. As used herein, the term “automatic” further includes predominantly automatic, that is, most of the operations (such as greater than 50%, for example) are performed by one or more hardware or software controlled machines with no human intervention such as user inputs to a graphical user selection interface, and the remainder of the operations (less than 50%, for example) are performed manually, that is, the manual operations are performed by one or more hardware or software controlled machines with human intervention such as user inputs to a graphical user selection interface to direct the performance of the operations.
Many of the functional elements described in this specification have been labeled as “logic,” in order to more particularly emphasize their implementation independence. For example, a logic element may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A logic element may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.
A logic element may also be implemented in software for execution by various types of processors. A logic element which includes executable code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified logic element need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the logic element and achieve the stated purpose for the logic element.
Indeed, executable code for a logic element may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, among different processors, and across several memory devices. Similarly, operational data may be identified and illustrated herein within logic elements, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices.
In the illustrated embodiment, a copy relationship identifies a source storage location, such as a primary storage location, and a target storage location, such as a secondary storage location, in which data stored at the source storage location is to be replicated or otherwise copied to the target storage location. Thus, as used herein, a source storage location and a target storage location are storage locations related by a copy relationship.
Furthermore, as used herein, the term “storage unit” refers to a storage location containing one or more units of data storage such as one or more volumes, cylinders, tracks, segments, extents, or any portion thereof, or other unit or units of data suitable for transfer. Thus, a source storage unit and the associated target storage unit may each be a storage volume. However, it is appreciated that a source storage unit and a target storage unit may each be of a size other than a volume, for example.
Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.
In the configuration illustrated in
In a particular copy relationship, the source unit is often referred to as the primary and the target unit is often referred to as the secondary. Replication relationships are defined between storage units of the data storage 10a and 10b. Notwithstanding a reference to the data storage 10a as “primary” and the data storage 10b as “secondary,” particular storage units of the data storage 10a and the storage 10b may play both a primary (or source role) and a secondary (or target role) depending upon the particular copy relationship.
As noted above, the computing environment includes one or more hosts 2a, 2b, 2n (
The primary storage controller 4a is located at a first site and the secondary storage controller 4b is located at a second site which may be geographically or functionally remote from the first site. Thus, in this example, the first site may be at a local site and the second site may be at geographically remote sites separated by a short or long geographical distance from the local site and from each other. Alternatively, the local and remote site may be relatively close such as in different buildings in the same general geographical location, in different rooms of the same building, in different machines in the same room, or in different portions or partitions of the same machine, of the network 6.
A typical host as represented by the host 2a (
Referring to
In the illustrated embodiment, the storage manager 232 including the data replication logic 234, is depicted as software stored in the memory 230 and executed by the CPU complex 12. However, it is appreciated that the logic functions of the storage manager 232 may be implemented as hardware, software, firmware or combinations of one or more thereof, depending upon the particular application.
One or more copy relationships 240, which may be maintained by the data replication logic 234 for the primary and secondary storage controllers 4a, 4b (
In the illustrated embodiment, a copy relationship 240 comprises a peer-to-peer mirror relationship for a pair of storage locations in which updates to the primary (source) storage locations of the mirror relationship 240 are mirrored to the secondary (target) storage locations of the mirror relationship 240. It is appreciated that other types of copy relationships may be established, depending upon the particular application. For example, the copy relationships 240 may include point-in-time snap copy relationships.
In connection with a copy relationship 240 in an asynchronous data replication mode of the data replication logic 234, updates to the primary storage locations of the primary storage 10a may be indicated in a bitmap of a set of bitmaps 244, which is an out-of-sync (OOS) bitmap in the illustrated embodiment. Bits of the OOS bitmap are cleared as the storage manager 232 copies updates indicated in the OOS bitmap to the corresponding storage locations of the secondary storage 10b of secondary storage control unit 4b.
The storage manager 232 accesses updates to the primary storage 10a to write to the corresponding storage locations in the storage 10b. In some applications, the copying and relationship functions may be performed by devices external to the storage systems 24a, 24b (
Periodically, volumes in a relationship 240 may be configured into a consistency group by the data replication logic 234 to ensure that a group of updates made to volumes at the primary system are also eventually made on the volumes of the consistency group to maintain data consistency as of a particular point in time or a particular set of data for those volumes of the group. Accordingly, additional updates to an OOS bit map may be stopped at a particular point in time to form a consistency group of volumes of the secondary system with respect to volumes of the primary system as of a particular point-in-time. Any unprocessed updates as indicated by the OOS bit map are transferred to the secondary storage so that the volumes of the consistency group are consistent as of the point in time at which updates were no longer added to the OOS bit map.
The interval of time of the consistency group formation process in which incremental updates indicated by the OOS bitmap are copied to the secondary storage and the OOS bitmap is updated (bits reset) to indicate such transfer, is referred to as “draining” the OOS bitmap. A second bitmap referred to as a Change Recording bitmap maintains a record of the tracks of the source volume that were updated (changed) during the consistency group drain time. When a consistency group is completed, the OOS bitmap of the consistency group is all zeros and the Change Recording bitmap indicates the updated tracks that were held back for the next consistency group. At this time, the Change Recording bitmap becomes the OOS bitmap for the mirror relationship and these updated tracks are mirrored to the remote volume along with any other updates that happen until the next consistency group is formed. The period following the draining interval until the next consistency group is formed, is referred to as an idle period for consistency group formation.
In contrast to the asynchronous mode, in a synchronous mode, an I/O operation which performed a write operation to the primary storage 10a is not considered complete until the mirror operation is completed, that is, it is not complete until the update data has been successfully replicated to the secondary storage 10b. Should the mirror operation fail such that the update is not successfully mirrored to the storage 10b, the host may be notified that the update operation was not successfully completed.
The storage manager 232 in one embodiment may transfer data from the primary storage 10a to the secondary storage 10b in tracks. As used herein, the term track may refer to a track of a disk storage unit but may also reference to other units of data configured in the storage 10a, 10b, such as a bit, byte, word, segment, page, block (such as a Logical Block Address (LBA)), etc., which may be a part of a larger grouping of data units, such as a volume, logical device, etc.
In one embodiment, the storage devices 10a, 10b may be comprised of one or more sequential access storage devices, such as hard disk drives and magnetic tape or may include non-sequential access storage devices such as solid state drives (SSD), for example. Each storage device 10a, 10b may comprise a single sequential or non-sequential access storage device or may comprise an array of storage devices, such as a Just a Bunch of Disks (JBOD), Direct Access Storage Device (DASD), Redundant Array of Independent Disks (RAID) array, virtualization device, tape storage, flash memory, etc.
One mode of the data replication logic 234 managing the copy relationships, may be implemented with asynchronous copy operations, such as a peer-to-peer remote copy (PPRC) program modified as appropriate in accordance with present description. An example of a PPRC program is the IBM Tivoli Productivity Center for Replication copy program that enables the switching of updates from the primary storage 10a to the secondary storage 10b. Suitable asynchronous mirroring programs include XRC (or zGM) modified as appropriate in accordance with present description. The described operations may be implemented with other programs such as other copy programs or other global recovery programs modified as appropriate in accordance with present description.
The system components 2a, 2b . . . 2n, 4, 4a, 4b, 10, 10a, 10b are connected to the network 6 which enables communication among these components. Thus, the network 6 includes a fabric which may comprise a Storage Area Network (SAN), Local Area Network (LAN), Intranet, the Internet, Wide Area Network (WAN), peer-to-peer network, wireless network, arbitrated loop network, etc. Communication paths from the storage subsystems to the hosts 2a, 2b, . . . 2n may be based upon a particular host attachment protocol such as Fibre Connection (FICON), for example. Other communication paths of the fabric may comprise for example, a Fibre Channel arbitrated loop configuration, a serial loop architecture or a bus interface, such as a Peripheral Component Interconnect (PCI) interface such as a PCI-Express interface. The communication paths of the fabric may also be part of an Ethernet network, for example, such that each node has an individual network (internet protocol) address. Other types of communication paths may be utilized, such as a modem telephone path, wireless network, etc., depending upon the particular application.
Communication software associated with the communication paths includes instructions and other software controlling communication protocols and the operation of the communication hardware in accordance with the communication protocols, if any. It is appreciated that other communication path protocols may be utilized, depending upon the particular application.
In this embodiment, the data replication logic 234 includes asynchronous data mirroring logic 310 configured to asynchronously mirror data from a first data unit such as a primary volume 1 (
In the example of
Asynchronous mirroring of data from a primary volume 1′ to a secondary volume 2′ is represented by an arrow labeled “mirror relationship 1′”. The data mirroring logic 310 of the data replication logic 234 in mirroring data from the primary volume 1′ to the secondary volume 2′, is further configured to generate a remote out-of-synch (OOS) bitmap 1′ of bitmaps 244a (
As previously mentioned, incremental updates to the primary storage locations of the primary storage 10a may be indicated in an out-of-sync (OOS) bitmap 1 (
In the example of
This draining interval (CG1 draining) is complete once the OOS bitmap 1 (
Once the remote mirror snap copy has been established as indicated in the timeline of
For example, the draining interval, CG1 draining, is complete once the OOS bitmap 1 for consistency group CG1 is fully drained as shown in
The consistency group logic 311 (
In one aspect of the present description, the local-remote pair of snap copy relationships established in response to the local-remote pair establish command are assigned a snap copy sequence number, such as the snap copy sequence number SC_CG0 in the example of
In this embodiment, the snap copy generation logic 314 further includes sequence number determination logic 334 (
The local-remote pair of snap copy relationships established in response to the local-remote pair establish command 0 further include a remote point-in-time snap copy relationship as represented by an arrow labeled “PIT snap copy relationshipCG0_R” in the secondary storage system 24b (
The snap copy generation logic 314 (
Conversely, in one aspect of the present description, the establishment of the remote point-in-time snap copy relationship of the local-remote pair of snap copy relationships may be delayed as a function of the state of the consistency group formation process in progress at the time of receipt of the local-remote pair snap copy establish command. However, notwithstanding a delay in the establishment of the remote point-in-time snap copy relationship of the local-remote pair of snap copy relationships, both snap copy relationships, local and remote, of the local-remote pair of snap copy relationships may be reported to the host which issued the local-remote snap copy pair establish command as established even though the remote snap copy relationship may not yet have been established but instead may have been delayed.
Thus, the snap copy generation logic 314 (
In one embodiment, the plurality of states includes an idle state such as the idle state “CG0 idle” in the example of
In connection with potential delay of establishment of the remote point-in-time snap copy relationship, command logic 350 (
In one embodiment, the command logic 350 of the data replication logic 234 is configured to issue a resource reservation command to the secondary storage controller 4b in response to the local-remote pair snap copy establish command, to reserve resources of the secondary storage system for subsequent establishment of the remote point-in-time snap copy relationship of the local-remote pair. Further in response to the resource reservation command, the determined snap copy sequence number (block 318,
The state determination logic 344 (
In the example of
Because the state of the consistency group formation process for consistency group CG0 was in an idle state (CG0 Increment Complete) when the local-remote pair snap copy establish command 0 was received, the volume 2 of the consistency group CG0 is consistent with respect to volume 1 of the primary system when the local-remote pair snap copy establish command 0 was received. Accordingly, the local snap copy volume 1′ will be consistent with the remote snap copy volume 2′. Accordingly, the remote snap copy volume 2′ may be established without significant delay in response to the local-remote pair snap copy establish command 0.
Conversely, the delay logic 348 delays (block 364,
In the example of
The snap copy generation logic 314 initiates and establishes (block 340,
The local-remote pair of snap copy relationships established in response to the local-remote pair establish command 1 eventually will include a remote point-in-time snap copy relationship as represented by an arrow labeled “PIT snap copy relationshipCG1_R” (
In connection with potential delay of establishment of the remote point-in-time snap copy relationship, the command logic 350 (
Further in response to the resource reservation command, the determined snap copy sequence number (block 318,
In the example of
Thus, in the example of the local-remote pair snap copy establish command 1 of
Because the state of the consistency group formation process for consistency group CG1 was in a draining state (CG1 draining) when the local-remote pair snap copy establish command 1 was received, the volume 2 of the consistency group CG1 is not consistent with respect to volume 1 of the primary system when the local-remote pair snap copy establish command 1 was received. Accordingly, the local snap copy volume 1′ will not be consistent with a remote snap copy volume 2′. Accordingly, establishment of the remote snap copy volume 2′ will be delayed.
The reservation interval for delaying the establishing of the remote snap copy of the local-remote pair ends once the increment portion of the consistency group formation process of consistency group CG1 is complete as indicated by the point-in-time “increment complete” for the consistency group CG1 being formed. As previously mentioned, the CG1 draining interval is complete once the OOS bitmap 1 for the consistency group is fully drained such that all incremental updates of the consistency group CG1 have been successfully copied from the primary storage volume 1′ to the secondary storage volume 2′ and as a result, all bits of the OOS bitmap 1 have been reset as shown in
Upon completion of the draining interval of consistency group CG1, the remote mirror snap copy formed at the point-in-time “remote mirror snap copy establish for CG1” is assigned a sequence number “CG1” as indicated in the timeline of the embodiment of
The state determination logic 344 (
Accordingly, the delay logic 348 terminates (block 370,
Because the state of the consistency group formation process for consistency group CG1 was in a draining state (CG1 draining) when the local-remote pair snap copy establish command 1 was received, the establishment of the remote snap copy volume 2′ was delayed until the volume 2 of the consistency group CG1 is consistent with respect to volume 1 of the primary system. As a result, the local snap copy volume 1′ will be consistent with the remote snap copy volume 2′. Accordingly, the remote snap copy volume 2′ is established after the consistency group CG1 is complete.
In another example of 6, a local-remote pair snap copy establish command 2 was received (block 316,
The consistency group logic 311 stores the consistency group sequence number CG2 and the state “draining” of the consistency group formation process in progress in corresponding sequence number and state fields of a data structure such as the consistency group formation data structure 312. The local-remote pair of snap copy relationships established in response to the local-remote pair establish command 2 are assigned (block 318,
A local point-in-time snap copy relationship is established (block 340,
The snap copy generation logic 314 initiates and establishes (block 340,
The local-remote pair of snap copy relationships established in response to the local-remote pair establish command 2 eventually will include a remote point-in-time snap copy relationship in the secondary storage system 24b from a data unit as a snap copy source, to another data unit as a snap copy target in the secondary storage system 24b. As described above, in one aspect of the present description, the establishment of the remote point-in-time snap copy relationship of the local-remote pair of snap copy relationships, may be delayed as a function of the state of the consistency group formation process in progress at the time of receipt of the local-remote pair establish command.
In connection with potential delay of establishment of the remote point-in-time snap copy relationship, the command logic 350 (
Further in response to the resource reservation command, the determined snap copy sequence number (block 318,
In the example of the local-remote pair snap copy establish command 2 of
The reservation interval for delaying the establishing of the remote snap copy of the local-remote pair ends once the increment portion of the consistency group formation process of consistency group CG2 is complete (indicated by the point-in-time “increment complete”) for the consistency group CG2 being formed. As previously mentioned, the CG2 draining interval is complete once the OOS bitmap for the consistency group is fully drained such that all incremental updates of the consistency group CG2 have been successfully copied from the primary storage volume to the secondary storage volume and as a result, all bits of the OOS bitmap have been reset.
Upon completion of the draining interval of consistency group CG2, the remote mirror snap copy formed at the point-in-time “remote mirror snap copy establish for CG2” is assigned a sequence number “CG2” as indicated in the timeline of the embodiment of
At that point, the state determination logic 344 (
Accordingly, the delay logic 348 terminates (block 370,
In one embodiment, the local-remote pair point-in-time snap copy command which generates the point-in-time snap copies may be of a “no background copy” type in which the content of the source volume need not be transferred to the point-in-time snap copy target volume in a background copy operation. Instead, a read operation directed to a track of the point-in-time snap copy target volume may be redirected to the corresponding track of the source volume to obtain the content of that track if the target bitmap indicates by a bit state value “1” that the track has not been transferred to the point-in-time snap copy target volume. However, should a track of the source volume be targeted for an update, the content of that track will be transferred to the corresponding track of the point-in-time snap copy target volume and the associated target bitmap will be updated to indicate that the content of that track has been transferred. Accordingly, data for the target to provide a consistent point-in-time snap copy of the data of the source volume as of the first point-in-time may be obtained by data transfers within the associated local or remote system.
It is appreciated that in other embodiments, the local-remote pair point-in-time snap copy command which generates the point-in-time snap copies may a “background copy” type in which the content of the source volume is transferred in a background copy operation to the point-in-time snap copy target volume. As the content of each track of the source volume is transferred in a background copy to the content of the corresponding track of the point-in-time snap copy target volume, the bit state of the bit representing that track in the associated target bitmap may be updated to a bit state value “0” to indicate that the track has been transferred to the point-in-time snap copy target volume.
Thus, as used herein, the term “copying” includes actual copying in which data content of a source storage location is actually transferred to a target storage location. However, the term “copying” as used herein also includes virtual copying in which a data structure such as a bitmap is set to redirect read operations initially directed to a target storage location, to a source storage location instead of the target storage location, and thus need not include actual transfer of the data content of a source storage location to a target storage location. Similarly, as used herein, the term “copy” includes an actual copy in which a target storage location contains the same data content as a source storage location but also includes a virtual copy in which a target storage location has an associated data structure such as a target bitmap which has been set to redirect read operations initially directed to the target storage location, to the source storage location instead of the target storage location, such that a virtual copy need not include the actual data content of the source storage location.
In one aspect of the present description, it is appreciated that once the consistency group has completed, data for the remote point-in-time snap copy volume 2′ already resides on the secondary system 24b due to the mirroring operation as represented by the mirror relationship 1 (
The computational components of the figures may each be implemented in one or more computer systems, such as the computer system 1002 shown in
As shown in
Computer system/server 1002 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server 1002, and it includes both volatile and non-volatile media, removable and non-removable media.
System memory 1006 can include computer system readable media in the form of volatile memory, such as random access memory (RAM) 1010 and/or cache memory 1012. Computer system/server 1002 may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system 1013 can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). Although not shown, a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to bus 1008 by one or more data media interfaces. As will be further depicted and described below, memory 1006 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the invention.
Program/utility 1014, having a set (at least one) of program modules 1016, may be stored in memory 1006 by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. The components of the computer 1002 may be implemented as program modules 1016 which generally carry out the functions and/or methodologies of embodiments of the invention as described herein. The system of
Computer system/server 1002 may also communicate with one or more external devices 1018 such as a keyboard, a pointing device, a display 1020, etc.; one or more devices that enable a user to interact with computer system/server 1002; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server 1002 to communicate with one or more other computing devices. Such communication can occur via Input/Output (I/O) interfaces 1022. Still yet, computer system/server 1002 can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter 1024. As depicted, network adapter 1024 communicates with the other components of computer system/server 1002 via bus 1008. It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computer system/server 1002. Examples, include, but are not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc.
The reference characters used herein, such as i, j, and n, are used to denote a variable number of instances of an element, which may represent the same or different values, and may represent the same or different value when used with different or the same elements in different described instances.
The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.
The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.
Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.
Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.
Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.
These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.
The terms “an embodiment”, “embodiment”, “embodiments”, “the embodiment”, “the embodiments”, “one or more embodiments”, “some embodiments”, and “one embodiment” mean “one or more (but not all) embodiments of the present invention(s)” unless expressly specified otherwise.
The terms “including”, “comprising”, “having” and variations thereof mean “including but not limited to”, unless expressly specified otherwise.
The enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise.
The terms “a”, “an” and “the” mean “one or more”, unless expressly specified otherwise.
Devices that are in communication with each other need not be in continuous communication with each other, unless expressly specified otherwise. In addition, devices that are in communication with each other may communicate directly or indirectly through one or more intermediaries.
A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary a variety of optional components are described to illustrate the wide variety of possible embodiments of the present invention.
When a single device or article is described herein, it will be readily apparent that more than one device/article (whether or not they cooperate) may be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device/article may be used in place of the more than one device or article or a different number of devices/articles may be used instead of the shown number of devices or programs. The functionality and/or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments of the present invention need not include the device itself.
The foregoing description of various embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims herein after appended.
