Patent Application
20070180214
The present disclosure relates generally to computer systems and information handling systems, and, more particularly, to a system and method for dynamic striping in a storage array.
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to these users is an information handling system. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may vary with respect to the type of information handled; the methods for handling the information; the methods for processing, storing or communicating the information; the amount of information processed, stored, or communicated; and the speed and efficiency with which the information is processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include or comprise a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
An information handling system or computer system may be coupled to a network that that includes a fault tolerant storage array. One example of a fault tolerant storage array is RAID storage. RAID storage typically involves a storage array comprised of several disks. The disks are collectively managed by a storage controller. RAID storage arrays are characterized by the ability to restore or rebuild the information on a drive following a failure. On the disks of the array, data is saved in the form of stripes, which extend across each of the disks of the array. A single stripe is typically comprised of stripe elements or strips. If a stripe includes only a single strip in each disk, the stripe has a depth of one. If the stripe includes three strips in each disk, the stripe has depth of three. The size of a stripe is defined as the depth of the stripe times the number of disks in the stripe. In the previous example, if the stripe depth is three and there are three disks in the stripe, the stripe size is nine. An array may include multiple stripes, and each stripe may be accessed by multiple applications. Depending on the data access patterns of the various applications that access a particular stripe, it may not be most efficient for each stripe of the array to have the same stripe size.
In accordance with the present disclosure, a system and method is disclosed that provides for the dynamic striping of the disks of a storage array. The system and method disclosed herein provides a technique for translating access commands in a manner that is specific to the stripe that is the target of the access command. When a storage controller receives the access command, the storage controller identifies the logical block that is the subject of the access command. The storage controller identifies the stripe that includes the logical block. On the basis of the identification of the stripe, the storage controller retrieves a stripe-specific translation function, the input of which is the logical address of the access command. After the storage controller executes the stripe-specific translation function, the storage controller completes the access command at the translated address.
The system and method disclosed herein is technically advantageous because it provides a technique that allows a single array to include stripes of varying sizes. As such, the stripes of the array can be sized to best accommodate the characteristics of the applications accessing the stripes or the data content of the stripes. The system and method provides for stripe-specific translation functions, each of which is associated with a stripe and performs the step of translating logical to physical addresses according to the parameters of the associated stripe.
Another technical advantage of the system and method disclosed herein is that the mapping functions are stored in a location that is immediately accessible to the processing resources of the storage controller. As such, the storage controller can easily access the mapping table and the mapping functions without the necessity of accessing a storage location that is exterior to the storage controller. Other technical advantages will be apparent to those of ordinary skill in the art in view of the following specification, claims, and drawings.
A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communication with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.
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The RAID array in the example of
Because the stripes of the array are not of a uniform size, a mapping function is associated with each of the stripes. Shown in
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If it is determined at step 30 that the access command is a write command, the controller at step 40 determines the optimal stripe size for the write command. The determination of the optimal stripe size for the write command can be determined on the basis of several factors, including the type of application that issued the write command and the amount of data to be written as part of the write command. Once the controller identifies the optimal stripe for the write command, the controller determines identifies a stripe that has the stripe size that is closet to the determined optimal stripe size. The selected stripe can be an existing stripe of a new stripe. A new stripe is a stripe that has not yet been written to. If it is determined at step 42 that the selected stripe is a new stripe, the stripe size and the range of logical blocks associated with the stripe is saved at step 44 to the storage location in the storage controller. After the parameters of the stripe are saved to the storage location in the storage controller, the storage controller computes at step 46 the physical address associated with the target of the write operation. Likewise, if it is determined at step 42 that the selected stripe is not a new stripe, the storage controller computes the physical address associated with the target of the write operation at step 46.
The computation of the physical address associated with the logical address of the write command involves the selection and execution the function associated with the stripe. The input to the function is the logical address of the write command. Once the physical address is determined from the function, the write operation is completed at step 48 with the physical address of the access command. As such, once the stripe has been identified, a stripe-specific mapping function is executed to generate the physical address associated with the logical address of the write command.
It should be recognized that the system and method disclosed herein is not limited in its application to RAID arrays. Rather, this system could be implemented with reference to any array of disks that stores data in stripes of varying size. Although the present disclosure has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and the scope of the invention as defined by the appended claims.
