Parallel migration of multiple consistency groups in a storage system

Abstract

Described embodiments provide systems and processes for performing data migration in a storage system. One or more consistency groups are migrated from at least one source device to at least one target device in the storage system. The consistency groups are replicated from the source device to the target device by an asynchronous data replication operation from the source device to the target device and one or more synchronous data replication operations from the source device to the target device if data stored on the source device is changed. The consistency groups are operated on the source device and the target device in an active-active mode, wherein the source device and target device are active and accessible by host devices. Replicated consistency groups are determined to include in a cutover operation that is performed by deactivating the at least one source device associated with the included consistency groups.

Description

BACKGROUND

Computer data is increasingly vital to modern organizations, and protecting against data loss in the event of a system failure is an increasingly important organization objective. Data protection systems for storing organizational source (e.g., production) site data on a periodic basis suffer from several drawbacks. First, they require a system shutdown during backup, since the data being backed up cannot be used during the backup operation. Second, they limit the points in time to which the production site can recover. For example, if data is backed up on a daily basis, there may be several hours of lost data in the event of a disaster. Third, the data recovery process itself is both time consuming and can consume system resources.

Some data protection systems use data replication, by creating a copy of the organization's production site data on a secondary backup storage system, and updating the backup with changes. The backup storage system may be situated in the same physical location as the production storage system, or in a physically remote location. Data replication systems generally operate either at the application level, at the file system level, at the hypervisor level or at the data block level.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

One aspect may provide a process for performing data migration in a storage system. One or more consistency groups may be migrated from at least one source device to at least one target device in the storage system. The consistency groups may be replicated from the source device to the target device by an asynchronous data replication operation from the source device to the target device and one or more synchronous data replication operations from the source device to the target device if data stored on the source device is changed. The consistency groups may be operated on the source device and the target device in an active-active mode, wherein the source device and target device may be active and accessible by host devices. Replicated consistency groups may be determined to include in a cutover operation that is performed by deactivating the at least one source device associated with the included consistency groups.

Another aspect may provide a system including a processor and memory that stores computer program code that when executed on the processor causes the processor to execute a data migration operation to migrate data from at least one source volume to at least one target volume in a storage system. One or more consistency groups may be replicated from the source device to the target device by performing an asynchronous data replication operation from the source device to the target device and performing one or more synchronous data replication operations from the source device to the target device if data stored on the source device is changed. The consistency groups may be operated on the source device and the target device in an active-active mode. In the active-active mode, the source device may be active and accessible by one or more host devices, and the target device may also be active and accessible by one or more host devices. One or more replicated consistency groups are selected to include in a cutover operation. The cutover operation may be performed by deactivating the source device associated with the included consistency groups.

Another aspect may provide a computer program product including a non-transitory computer readable storage medium having computer program code encoded thereon that when executed on a processor of a computer causes the computer to execute a data migration operation to migrate data from at least one source volume to at least one target volume in a storage system. One or more consistency groups may be replicated from the source device to the target device by performing an asynchronous data replication operation from the source device to the target device and performing one or more synchronous data replication operations from the source device to the target device if data stored on the source device is changed. The consistency groups may be operated on the source device and the target device in an active-active mode. In the active-active mode, the source device may be active and accessible by one or more host devices, and the target device may also be active and accessible by one or more host devices. One or more replicated consistency groups may be selected to include in a cutover operation. The cutover operation may be performed by deactivating the source device associated with the included consistency groups.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Objects, aspects, features, and advantages of embodiments disclosed herein will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements. Reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features. For clarity, not every element may be labeled in every figure. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments, principles, and concepts. The drawings are not meant to limit the scope of the claims included herewith.

FIG. 1 is a block diagram of an example of a storage system to perform data replication from a source to a target in accordance with an illustrative embodiment;

FIG. 2 is a block diagram of another example of a storage system to perform data replication from a source to a target in accordance with an illustrative embodiment;

FIG. 3 is a flow diagram of an example of a process to perform data migration from a source to a target in accordance with an illustrative embodiment;

FIG. 4 is a flow diagram of an example of a process to migrate selected consistency groups for the data migration process of FIG. 3 in accordance with an illustrative embodiment;

FIG. 5 is a block diagram of an example of a hardware device that may perform at least a portion of the processes in FIGS. 3 and 4.

DETAILED DESCRIPTION

FIG. 1 shows an example storage system 100 that may perform data migration operations, in accordance with illustrative embodiments.

Storage system 100 may include at least one source site 102 and at least one target site 112, which may be co-located or geographically separated. Source site 102 may include one or more processors 105, storage application 106, and storage 108. In some embodiments, storage 108 may include one or more storage volumes 135_1-S, that operate as active or production volumes. Target site 112 may include replica manager 116 that manages a plurality of replicas 118_1-N (generally referred to herein as replicas 118) according to a policy 114 (e.g., a replication and/or retention policy). Replicas 118 may be stored in one or more volumes 139_1-Z of storage 137 of target site 112. Target site 112 may also include one or more processors 133. Source site 102 and target site 112 may be in communication with one or more hosts 113 via communication links 111 and 115, respectively.

Hosts 113 may perform input/output (I/O) operations on source-side storage 108 (e.g., read data from and write data to storage 108). In some embodiments, the I/O operations may be intercepted by and controlled by storage application 106. As changes are made to data stored on storage 108 via the I/O operations from hosts 113, or over time as storage system 100 operates, storage application 106 may perform data migration 121 from source site 102 to target site 112 over communication link 110. In some embodiments, communication link 110 may be a long distance communication link of a storage area network (SAN), such as an Ethernet or Internet (e.g., TCP/IP) link that may employ, for example, the iSCSI protocol. In some embodiments, one or both of source site 102 and/or target site 112 may include internal (e.g., short distance) communication links (shown as communication links 109 and 119) to transfer data between storage volumes 139_1-Z of storage 137 for storing replicas 118_1-N, such as an InfiniBand (IB) link or Fibre Channel (FC) link.

In illustrative embodiments, storage system 100 may employ a snapshot (or replication) mechanism to replicate data between source site 102 and target site 112. A replica (or snapshot) may be created from data within storage 108 and transferred to one or more target sites 112 during a data replication cycle that may be performed based on data replication policies (e.g., policy 114) that may define various settings for data recovery operations. A data replication cycle may be asynchronous data replication performed at time-based intervals during operation of storage system 100, or may alternatively be synchronous data replication performed when data is changed on source site 102.

Storage system 100 may include one or more consistency groups. A consistency group 147 may include one or more volumes 135 of source site 102, each associated with a corresponding volume 139 of target site 112. Consistency group 147 may treat source volumes 135 and target volumes 139 as a single logical entity for data replication and migration. Each volume 139 may store one or more associated replicas 118 that reflect the data in the consistency group 147 at a point in time (e.g., when the replica 118 was created). For example, replicas (e.g., snapshots) 118 may be generated for each source volume 135 of consistency group 147 at the same time, and stored on associated ones of target volumes 139. As shown in FIG. 1, an illustrative consistency group 147 may include two source volumes 135₁ and 135₂ (135 generally) and two target volumes 139₁ and 139₂ (139 generally). Each target volume 139 may include one or more replicas 118. For example, volume 139₁ may include replicas 118_1,1-118_1,N, volume 139₂ may include replicas 118_2,1-118_2,N, and volume 139_Z may include replicas 118_Z,1-118_Z,N. In some embodiments, replicas 118 for respective source volumes 135 of consistency group 147 may be grouped into sets (e.g., a snapshot set or snapset). Thus, as illustrated in FIG. 1, replica 118_1,1 created for source volume 135₁, and replica 118_2,1 created for source volume 135₂ of consistency group 147 may be included in snapset 145.

Illustrative embodiments may migrate data from one or more volumes 135_1-S of source site 102 to one or more volumes 139_1-Z of storage 137 of target site 112 in a “seamless” manner, shown as data migration 121. For example, data migration operation 121 may be said to be seamless if data is migrated from a first set of volumes of source site 102 (e.g., a first set of volumes 135_1-S) to a second set of volumes 139_1-Z of storage 137 of target site 112 while the storage system is operating and without the migrated data being unavailable to storage system 100 for other input/output (I/O) operations such as reads or writes. In other words, relocation of the data from source site 102 to target site 112 is “invisible” to users of the storage system in that the storage system is operable throughout data migration operation 121. In some embodiments, the migrated data may include snapshots (or replicas) created for data recovery.

Once the data is moved from source site 102 to target site 112 (including SCSI “personalities” of the source volumes), hosts 113 may connect to volumes 139_1-Z of target site 112, and the volumes 135_1-S of source site 102 can be deactivated (e.g., cutover). In some embodiments, a SCSI personality of a given volume may include meta-data associated with the volume. The meta-data may include, for example, one or more properties of the given volume (e.g., size, block size, transfer size, one or more features supported by the volume, etc.), one or more identifiers associated with the given volume (e.g., a volume serial number, a volume address, or vendor information of the volume) and dynamic state information of the volume (e.g., SCSI reservation state information of the volume, Asymmetric Logical Unit Access (ALUA) state information of the volume, etc.). In some embodiments, the SCSI personality meta-data may be stored in one or more inquiry pages of the volume, such as Vital Product Data (VPD) information pages of the volume. During data migration operation 121, the SCSI personalities of given ones of target volumes 139_1-Z may be matched to the SCSI personalities of associated ones of source volumes 135_1-S.

In some embodiments, during data migration operation 121, storage system 100 may operate in an active/passive mode, where hosts 113 cutover from source site 102 to target site 112, such that only one of the source site 102 and the target site 112 is accessible by hosts 113. In some embodiments, during data migration operation 121, storage system 100 may operate in an active/active mode, where hosts 113 are allowed concurrent access to both source site 102 and target site 112. In the active/active mode, source site 102 (or one or more volumes 135 of source site 102) may later be disconnected and removed, and hosts 113 access only target site 112.

Referring to FIG. 2, in an illustrative embodiment, apparatus 206 may form part of system 200 and include memory 208 storing program logic 210, processor 212 for executing process 214, and communications I/O interface 218, connected via a bus 216 to allow communication between memory 208, processor 212 and devices external to apparatus 206. For example, in some embodiments, communications I/O interface 218 may be coupled to apparatus 206, external media 220, one or more I/O devices 222, and a display device 224. In some embodiments, communications I/O interface 218 may couple apparatus 206 to one or more source devices 202₁-202_X via network 204. In some embodiments, communications I/O interface 218 may couple apparatus 206 to one or more target devices 228₁-228_Y via network 226. In some embodiments, network 226 of FIG. 2 may be a communication fabric between volumes of targets 228. For example, in some embodiments, network 226 may be an InfiniBand (IB) network or a Fibre Channel (FC) network.

Referring to FIG. 3, process 300 is an example of a process to perform at least a part of a data migration operation of storage system 100 in accordance with illustrative embodiments. At block 302, the data migration operation of storage system 100 begins, for example when a data migration command is received by storage system 100. At block 304, storage system 100 may receive a selection of one or more consistency groups 147_1-Q of storage 108 to migrate to one or more volumes 139_1-Z of target site 112. In described embodiments, a consistency group may be a group of volumes 135_1-S and replicas 118 that are treated as a single entity for data replication and data migration. For example, a consistency group may be a group of volumes 135_1-S for which replicas 118 (e.g., snapshots) are generated at the same time. At block 306, data migration may be performed for the selected consistency groups (e.g., data of each consistency group is copied and stored on one or more corresponding target volumes 139_1-Z). Block 306 will be described in greater detail in conjunction with FIG. 4.

Although not shown in FIG. 3, after block 306, some embodiments may optionally perform a discovery operation to determine whether corresponding target volumes can be accessed by one or more host devices before performing a cutover operation (e.g., at block 310). For example, described embodiments may track which hosts 113 have recognized which target volumes (e.g., volumes 139_1-Z of target site 112) and, thus, may allow storage system 100 to complete a data migration by performing a cutover from a source to a target (e.g., deactivation of the source) once all host devices have recognized one or more target volumes 139_1-Z associated with selected consistency groups 147. For example, in an illustrative embodiment, the discovery operation may be performed as described in co-pending U.S. patent application Ser. No. 15/085,172 filed on common date herewith, entitled “DETECTION OF HOST CONNECTIVITY FOR DATA MIGRATION IN A STORAGE SYSTEM,” which is assigned to the same assignee as this patent application and is incorporated herein by reference in its entirety.

At block 310, storage system 100 may receive a selection of one or more consistency groups to include in a cutover operation and, at block 312, the cutover operation may be performed for the consistency groups selected at block 310. For example, a cutover operation from a source device to a target device may allow host access only to the target device and allow the source device to be deactivated. As indicated by block 314, block 312 may be iteratively repeated until the selected consistency groups have had the cutover operation performed. At block 314, once the selected consistency groups have had the cutover operation performed, at block 316 storage system 100 may determine whether the consistency groups have been successfully migrated. If, at block 316, one or more of the consistency groups have not been successfully migrated, then at block 318, storage system 100 may receive a request to re-attempt data migration for one or more volumes or consistency groups, and process 300 may repeat at block 306. Alternatively, at block 318, storage system 100 may receive a request to cancel data migration for one or more consistency groups (e.g., to determine a cause of the data migration failure, etc.). If, at block 316, the consistency groups have been successfully migrated, then at block 320, data migration process 300 completes.

Referring to FIG. 4, process 306′ is an example of a process to perform migration of selected consistency groups from source devices to target devices, in accordance with an illustrative embodiment. In some embodiments, process 306′ may be performed in a volume-by-volume manner. In such embodiments, process 306′ may be performed multiple times in parallel to perform data migration for each of the volumes (e.g., volumes 135_1-S of FIG. 1). At block 402, process 306′ starts. At block 404, an asynchronous (async) data replication operation may be performed to replicate data from source site 102 to target site 112. At block 406, one or more synchronous (sync) data replication operations may be performed as needed, for example when data is changed on source site 102 such that target site 112 includes up-to-date replicas. At block 408, source site 102 and target site 112 are operated in active-active mode. In described embodiments, in the active-active mode, source site 102 may be active and accessible by hosts 113, and target site 112 may also be active and accessible by hosts 113. Operation may continue in active-active mode until the cutover operation is performed at block 312 (FIG. 3), for example by receiving a selection of one or more consistency groups to include in the cutover operation. At block 410, migration operation 306′ completes.

Described embodiments may provide an automated process to perform application-by-application data migration processes individually and in parallel, allowing sharing of resources of storage system 100 and maximizing utilization of link 110. As described, some embodiments may start a data migration by performing an asynchronous date replication from source site 102 to target site 112. Synchronous data replication may be performed as necessary (e.g., as data is modified on source site 102). Source site 102 and target site 112 may be operated in an active-active mode where both source site 102 and target site 112 may be accessible to hosts 113, and data is updated to both source site 102 and target site 112 as data operations occur. A cutover operation from source site 102 to target site 112 may be performed after receiving confirmation (e.g., a selection of one or more consistency groups) to perform the cutover operation.

Described embodiments of storage system 100 may pause a data migration operation before performing a cutover operation (e.g., storage system 100 is operated with both source site 102 and target site 112 active). For example, a data migration process may be started for a large number (e.g., hundreds) of applications (or consistency groups) in parallel. As they are migrated, the applications (or consistency groups) may operate in the active-active mode on both source site 102 and target site 112 until receiving a selection of one or more of the applications (or consistency groups) to cutover to operate only on target site 112. The applications (or consistency groups) may then be cutover one-by-one. In other embodiments, storage system 100 may operate in asynchronous replication mode until receiving a selection of one or more of the applications (or consistency groups) to continue the migration process (e.g., to continue process 306′ from block 404 to block 406).

Referring to FIG. 5, in some embodiments, source site 102 and/or target site 112 are implemented as one or more computers. Computer 500 may include processor 502, volatile memory 504 (e.g., RAM), non-volatile memory 506 (e.g., a hard disk drive, solid state drive such as a flash drive, a hybrid magnetic and solid state drive, etc.), graphical user interface (GUI) 508 (e.g., a mouse, a keyboard, a display, and so forth) and input/output (I/O) device 520. Non-volatile memory 506 stores computer instructions 512, an operating system 516 and data 518 such that, for example, the computer instructions 512 are executed by the processor 502 out of volatile memory 504 to perform at least a portion of processes 300 and 306′ (FIGS. 3 and 4). Program code may be applied to data entered using an input device of GUI 508 or received from I/O device 520.

Processes 300 and 306′ (FIGS. 3 and 4) are not limited to use with the hardware and software of FIG. 5 and may find applicability in any computing or processing environment and with any type of machine or set of machines that is capable of running a computer program. Processes 300 and 306′ may be implemented in hardware, software, or a combination of the two.

The processes described herein are not limited to the specific embodiments described. For example, processes 300 and 306′ are not limited to the specific processing order shown in FIGS. 3 and 4. Rather, any of the blocks of processes 300 and 306′ may be re-ordered, combined or removed, performed in parallel or in serial, as necessary, to achieve the results set forth herein.

Processor 502 may be implemented by one or more programmable processors executing one or more computer programs to perform the functions of the system. As used herein, the term “processor” is used to describe an electronic circuit that performs a function, an operation, or a sequence of operations. The function, operation, or sequence of operations can be hard coded into the electronic circuit or soft coded by way of instructions held in a memory device. A “processor” can perform the function, operation, or sequence of operations using digital values or using analog signals. In some embodiments, the “processor” can be embodied in an application specific integrated circuit (ASIC). In some embodiments, the “processor” can be embodied in a microprocessor with associated program memory. In some embodiments, the “processor” can be embodied in a discrete electronic circuit. The “processor” can be analog, digital or mixed-signal.

While illustrative embodiments have been described with respect to processes of circuits, described embodiments may be implemented as a single integrated circuit, a multi-chip module, a single card, or a multi-card circuit pack. Further, as would be apparent to one skilled in the art, various functions of circuit elements may also be implemented as processing blocks in a software program. Such software may be employed in, for example, a digital signal processor, micro-controller, or general purpose computer. Thus, described embodiments may be implemented in hardware, a combination of hardware and software, software, or software in execution by one or more processors.

Some embodiments may be implemented in the form of methods and apparatuses for practicing those methods. Described embodiments may also be implemented in the form of program code, for example, stored in a storage medium, loaded into and/or executed by a machine, or transmitted over some transmission medium or carrier, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation. A non-transitory machine-readable medium may include but is not limited to tangible media, such as magnetic recording media including hard drives, floppy diskettes, and magnetic tape media, optical recording media including compact discs (CDs) and digital versatile discs (DVDs), solid state memory such as flash memory, hybrid magnetic and solid state memory, non-volatile memory, volatile memory, and so forth, but does not include a transitory signal per se. When embodied in a non-transitory machine-readable medium, and the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the method.

When implemented on a processing device, the program code segments combine with the processor to provide a unique device that operates analogously to specific logic circuits. Such processing devices may include, for example, a general purpose microprocessor, a digital signal processor (DSP), a reduced instruction set computer (RISC), a complex instruction set computer (CISC), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a programmable logic array (PLA), a microcontroller, an embedded controller, a multi-core processor, and/or others, including combinations of the above. Described embodiments may also be implemented in the form of a bitstream or other sequence of signal values electrically or optically transmitted through a medium, stored magnetic-field variations in a magnetic recording medium, etc., generated using a method and/or an apparatus as recited in the claims.

Various elements, which are described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. It will be further understood that various changes in the details, materials, and arrangements of the parts that have been described and illustrated herein may be made by those skilled in the art without departing from the scope of the following claims.

Claims

1. A method comprising: replicating one or more consistency groups from at least one source device to at least one target device in a storage system by: performing an asynchronous data replication operation from the at least one source device to the at least one target device; andperforming one or more synchronous data replication operations from the at least one source device to the at least one target device if data stored on the at least one source device is changed;operating the consistency groups on the at least one source device and the at least one target device in an active-active mode, wherein the at least one source device is active and accessible by one or more host devices, and the at least one target device is active and accessible by one or more host devices;determining one or more replicated consistency groups to include in a cutover operation; andperforming the cutover operation by deactivating the at least one source device associated with the included consistency groups.

2. The method of claim 1, wherein determining one or more replicated consistency groups to include in the cutover operation comprises receiving a selection of the one or more replicated consistency groups to include in the cutover operation.

3. The method of claim 2, further comprising operating in the active-active mode without performing the cutover operation until receiving the selection of one or more replicated consistency groups to include in the cutover operation.

4. The method of claim 3, wherein failures of the storage system are reduced by operating in the active-active mode without performing the cutover operation until receiving the selection of one or more replicated consistency groups.

5. The method of claim 1, further comprising, in the active-active mode, storing, on the at least one source device and the at least one target device, current data of the selected consistency groups.

6. The method of claim 1, wherein performing the cutover operation comprises receiving a selection to perform the cutover operation for one or more applications associated with each of the selected consistency groups.

7. The method of claim 6, further comprising performing the cutover operation for the selected applications in an application-by-application manner.

8. The method of claim 7, further comprising performing the cutover operation for the selected applications in a parallel application-by-application manner.

9. The method of claim 1, further comprising operating the storage system in a storage area network.

10. The method of claim 1, wherein each of the at least one source device and each of the at least one target device comprises at least one storage volume, each storage volume comprising a solid state storage device.

11. A system comprising: a processor; andmemory storing computer program code that when executed on the processor causes the processor to execute a data migration between at least one source device and at least one target device in a storage system operable to perform the operations of: replicating one or more consistency groups from at least one source device to at least one target device in a storage system by: performing an asynchronous data replication operation from the at least one source device to the at least one target device; andperforming one or more synchronous data replication operations from the at least one source device to the at least one target device if data stored on the at least one source device is changed;operating the consistency groups on the at least one source device and the at least one target device in an active-active mode, wherein the at least one source device is active and accessible by one or more host devices, and the at least one target device is active and accessible by one or more host devices;determining one or more replicated consistency groups to include in a cutover operation; andperforming the cutover operation by deactivating the at least one source device associated with the included consistency groups.

12. The system of claim 11, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of receiving a selection of the one or more replicated consistency groups to cutover.

13. The system of claim 12, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of operating in the active-active mode without performing the cutover operation until receiving the selection of one or more replicated consistency groups.

14. The system of claim 13, wherein failures of the storage system are reduced by operating in the active-active mode without performing the cutover operation until receiving the selection of one or more replicated consistency groups.

15. The system of claim 11, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of, in the active-active mode, storing, on the at least one source device and the at least one target device, current data of the selected consistency groups.

16. The system of claim 11, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of receiving a selection to perform the cutover operation for one or more applications associated with each of the selected consistency groups.

17. The system of claim 16, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of performing the cutover operation for the selected applications in an application-by-application manner.

18. The system of claim 17, wherein the memory stores computer program code that when executed on the processor causes the processor to further perform the operations of performing the cutover operation for the selected applications in a parallel application-by-application manner.

19. A computer program product including a non-transitory computer readable storage medium having computer program code encoded thereon that when executed on a processor of a computer causes the computer to execute a data migration process between at least one source device and at least one target device in a storage system, the computer program product comprising: computer program code for replicating one or more consistency groups from at least one source device to at least one target device in a storage system by: performing an asynchronous data replication operation from the at least one source device to the at least one target device; andperforming one or more synchronous data replication operations from the at least one source device to the at least one target device if data stored on the at least one source device is changed;computer program code for operating the consistency groups on the at least one source device and the at least one target device in an active-active mode, wherein the at least one source device is active and accessible by one or more host devices, and the at least one target device is active and accessible by one or more host devices;computer program code for determining one or more replicated consistency groups to include in a cutover operation; andcomputer program code for performing the cutover operation by deactivating the at least one source device associated with the included consistency groups.

20. The computer program product of claim 19, further comprising: computer program code for receiving a selection of the one or more replicated consistency groups to cutover; andcomputer program product for operating in the active-active mode without performing the cutover operation until receiving the selection of one or more replicated consistency groups.