Method and apparatus to support determining storage area unit size

An information system comprises a host computer; a management computer; and a storage system including a storage controller and a plurality of storage volumes, the storage system configured to provide thin provisioned volumes from the plurality of storage volumes to the host computer for input/output. Each thin provisioned volume includes a plurality of segments which are provided by chunks of the storage volumes in the storage system. The storage controller is configured to assign a chunk to a segment on demand, analyze effectiveness of different chunk sizes for a chunk to be assigned to a segment and provide a report of the analyzed effectiveness to the management computer, and determine a size of a chunk to be assigned to a segment based on input from the management computer after the management computer receives the report of analyzed effectiveness.

BACKGROUND OF THE INVENTION

The present invention relates generally to storage systems and, more particularly, to a method and an apparatus to support determining the unit size of storage area.

Recently, the use of thin provisioning has been popularized for storage systems. The thin provisioning technique can realize efficient use of storage area as well as reduction of management cost relating to the storage systems. With the thin provisioning, a storage system provides virtual volumes as storage areas to store data for computers. The storage system allocates and assigns physical areas to only locations having write access of the computers. Consequently, the total amount of used physical areas can be smaller than the total amount of virtual areas shown to the computers. The thin provisioning technique is disclosed, for example, in US2004/0162958, the entire disclosure of which is incorporated herein by reference.

In the above allocation and assignation, a “page” or a “chunk” is used as a unit for the allocation and assignation of storage area. Choosing the size of the chunk brings a trade-off between access performance and efficiency of the physical area usage. For example, a small size (i.e., small unit) provides high efficiency because any unused part of the assigned chunk will be relatively small, while the performance for sequential access is smaller than the performance involving a large size chunk because the frequency and total overhead of solving relation between the virtual area and the physical area can be large in the case of the small unit. Therefore the size of chunk should be selected with consideration for the trade-off regarding expected performance and expected efficiency. The performance and efficiency depend on usage (i.e., access pattern) of data stored in the volume. The usage can be different for each data (i.e., each location) in the volume.

BRIEF SUMMARY OF THE INVENTION

Exemplary embodiments of the invention provide a method and an apparatus to support determining the unit size of storage area. As mentioned above, the chunk size should be selected according to the tendency of usage of data from the trade-off point of view. Thus, in order to support determining the appropriate chunk size, a method and an apparatus to estimate the effectiveness of chunk size from the viewpoints such as area usage efficiency and performance is necessary. With the present invention, a storage system that provides thin provisioned volumes (TPVs) to the host computers has the capability to monitor the access characteristics of volumes, a capability to evaluate the effectiveness of various chunk sizes by referring to the monitored access characteristics, and the capability to provide or present the evaluation to a user so that the user can choose an appropriate chunk size for each volume. According to the decision regarding chunk size for a volume, the user can instruct to apply the selected chunk size of the volume to the storage system. The storage system applies the chunk size of the volume in response to the user's instruction. In one embodiment, the parameters regarding read/write access are recorded as the access characteristics mentioned above. With regard to applying the selected chunk size, in one embodiment, the storage system changes the chunk size of one TPV from the current chunk size to the specified chunk size. In another embodiment, the storage system can adopt the selected chunk size for the new TPV in the migration of data from a conventional (not thin provisioned) volume to the TPV as well as in the conversion between different TPVs.

In accordance with an aspect of the present invention, an information system comprises a host computer; a management computer; and a storage system coupled to the host computer and the management computer, the storage system including a storage controller and a plurality of storage volumes, the storage system being configured to provide thin provisioned volumes from the plurality of storage volumes to the host computer for input/output (I/O). Each thin provisioned volume includes a plurality of segments which are provided by chunks of the storage volumes in the storage system. The storage controller is configured to assign a chunk to a segment on demand. The storage controller is configured to analyze effectiveness of different chunk sizes for a chunk to be assigned to a segment and provide a report of the analyzed effectiveness to the management computer. The storage controller is configured to determine a size of a chunk to be assigned to a segment based on input from the management computer after the management computer receives the report of analyzed effectiveness.

In some embodiments, the input from the management computer to the storage controller is given by a user who determines whether to change a chunk size based on the report of analyzed effectiveness. The storage controller is configured to analyze effectiveness of different chunk sizes based on monitoring accesses to the storage volumes and updating access information and used area information for the storage volumes, the access information maintaining information regarding access characteristics of the storage volumes, the used area information identifying used areas and unused areas of the storage volumes. The access information includes one or more of: frequency of transcending segment boundary in per unit time for various segment sizes; access rate per unit time for each read I/O; access rate per unit time for each write I/O; average access length for each read I/O; or average access length for each write I/O. The storage controller is configured to analyze effectiveness of different chunk sizes based on used area information for the storage volumes, the used area information identifying used areas and unused areas of the storage volumes. The storage controller is configured to allocate a chunk from the storage volumes to a volume to receive write data in response to a write request so that the allocated chunk is a continuous physical area in the storage volumes.

In specific embodiments, the storage controller, in response to an instruction to change the chunk size to a new chunk size for a storage volume: checks mapping information between thin provisioned volumes and corresponding chunks to determine whether there are one or more chunks to be copied between chunks of different sizes to accomplish changing the chunk size; and if yes, then, secures one or more new chunks of the new chunk size; copies data in old chunks to the new chunks; and updates the mapping information.

In some embodiments, the storage controller, in response to an instruction to change the chunk size to a new chunk size for a volume: obtains a new thin provisioned volume having segments with corresponding chunks of a chunk size which is same as the new chunk size; reads data from the volume specified in the instruction; writes the read data to the new thin provisioned volume with maintaining correspondence; updates volume information to change a relation between volumes and volume identifiers by replacing the volume specified in the instruction with the new thin provisioned volume; and if the volume specified in the instruction is a thin provisioned volume, releases the volume by updating mapping information between thin provisioned volumes and corresponding chunks and pool information for managing whether a chunk is used or not.

In accordance with another aspect of the invention, a method of managing sizes of the chunks comprises analyzing effectiveness of different chunk sizes for a chunk to be assigned to a segment and providing a report of the analyzed effectiveness to the management computer; and determining a size of a chunk to be assigned to a segment based on input from the management computer after the management computer receives the report of analyzed effectiveness.

Another aspect of the invention is directed to a computer-readable storage medium storing a plurality of instructions for controlling a data processor to manage sizes of chunks in the information system. The plurality of instructions comprise instructions that cause the data processor to analyze effectiveness of different chunk sizes for a chunk to be assigned to a segment and providing a report of the analyzed effectiveness to the management computer; and instructions that cause the data processor to determine a size of a chunk to be assigned to a segment based on input from the management computer after the management computer receives the report of analyzed effectiveness.

These and other features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the following detailed description of the specific embodiments.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, reference is made to the accompanying drawings which form a part of the disclosure, and in which are shown by way of illustration, and not of limitation, exemplary embodiments by which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. Further, it should be noted that while the detailed description provides various exemplary embodiments, as described below and as illustrated in the drawings, the present invention is not limited to the embodiments described and illustrated herein, but can extend to other embodiments, as would be known or as would become known to those skilled in the art. Reference in the specification to “one embodiment,” “this embodiment,” or “these embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same embodiment. Additionally, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details may not all be needed to practice the present invention. In other circumstances, well-known structures, materials, circuits, processes and interfaces have not been described in detail, and/or may be illustrated in block diagram form, so as to not unnecessarily obscure the present invention.

Furthermore, some portions of the detailed description that follow are presented in terms of algorithms and symbolic representations of operations within a computer. These algorithmic descriptions and symbolic representations are the means used by those skilled in the data processing arts to most effectively convey the essence of their innovations to others skilled in the art. An algorithm is a series of defined steps leading to a desired end state or result. In the present invention, the steps carried out require physical manipulations of tangible quantities for achieving a tangible result. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals or instructions capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, instructions, or the like. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” “displaying,” or the like, can include the actions and processes of a computer system or other information processing device that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system's memories or registers or other information storage, transmission or display devices.

The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may include one or more general-purpose computers selectively activated or reconfigured by one or more computer programs. Such computer programs may be stored in a computer-readable storage medium, such as, but not limited to optical disks, magnetic disks, read-only memories, random access memories, solid state devices and drives, or any other types of media suitable for storing electronic information. The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs and modules in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform desired method steps. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. The instructions of the programming language(s) may be executed by one or more processing devices, e.g., central processing units (CPUs), processors, or controllers.

Exemplary embodiments of the invention, as will be described in greater detail below, provide apparatuses, methods and computer programs for determining the unit size of storage area in a storage system that provides thin provisioned volumes, from viewpoints such as area usage efficiency and performance. The invention enables the user to determine the appropriate chunk size for each data.

A. System Configuration

FIG. 1illustrates an example of a hardware configuration of an information system in which the method and apparatus of the invention may be applied. A storage system includes a storage controller110, a main processor111, a switch112, a host interface controller113, a memory200, a cache300, disk controllers400, a plurality of disks600, and backend paths601(e.g., Fibre Channel, SATA, SAS, iSCSI(IP)). The main processor111performs various processes regarding the storage controller100. The main processor111and other components use the following information stored in the memory200: mapping information210, pool information202, volume information203, access information204, used area information205, and segment size information206. The main processor111carries out the various processes by executing the following programs stored in the memory200: write process program211, read process program212, evaluation program213, and report program214. A plurality of volumes (e.g., logical units) provided by the storage system100are produced from a collection of areas in HDDs (Hard Disk Drives). They may be protected by storing parity code (i.e., by RAID configuration) or mirroring.

At least one host500and a management computer520are connected to the host interface113of the storage system100via the SAN (Storage Area Network)900(e.g., Fibre Channel, Fibre Channel over Ethernet, iSCSI(IP), etc.). The host500, management computer520, and storage controller110are connected to each other via the LAN (Local Area Network)902(e.g., IP network). The host500has a file system501, an operating system OS502, an application program503, and an agent program504. To execute these programs, the host500also has resources such as processor, memory, storage devices not shown inFIG. 1. The management computer520has a file system521, an OS522, and a management program523. To execute these programs, the host500also has resources such as processor, memory, storage devices not shown inFIG. 1.

B. Overview of Method to Provide Volumes

As described below, the storage system100provides TPVs and conventional (i.e., not thin provisioned) volumes.FIG. 2is a schematic diagram illustrating the structure and method to provide TPVs. The storage system100has pool volumes620and divides the pool volumes620into a number of areas called chunks690. The storage system100assigns a chunk690to a segment of a virtual volume, namely, a thin provisioning volume (TPV) on a write access. In other words, a physical storage area is assigned on demand. InFIG. 2, a TPV is constituted by multiple segments virtually, and a chunk690is allocated from the pool volume620and assigned to a segment (i.e., a fixed length area (page) of TPV). For example, chunk4is assigned to segment6inFIG. 2. That is, a TPV is a page-based volume. The size of the segments (i.e., the size of assigned chunks) can be different for each volume. The segment size information206maintains options for the segment size.FIG. 3shows an example of the segment size information206.

To achieve thin provisioning, the storage controller110uses the mapping information201and pool information202.FIG. 4shows an example of the mapping information201in the form of a table. The table presents columns of TPV ID, Segment ID, Assigned, Pool Volume ID, and Chunk ID. This information maintains mapping between chunks and segments of each volume. The status of assignation is “No” if no chunk is assigned to the segment. This information can be constructed as a list or directory of each element for faster search.

FIG. 5shows an example of the pool information202in the form of a table. The table presents columns of Pool Volume ID, Chunk Size, Chunk ID, Usage, TPV ID, and Segment ID. This information manages whether a chunk is used or not. By using this information, the storage controller110is able to find free (unused) chunks in a write process described below. This information also can be constructed as a list or directory of each element to search for a free chunk quickly.

The storage system100also provides conventional volumes. The storage controller110allocates storage areas to the whole area of a conventional volume630at creation of the volume. In order to manage the storage area for conventional volumes, the storage controller110uses the volume information203.

FIG. 6shows an example of the volume information203in the form of a table. The table presents columns of Volume ID, Type, Size, Conventional Volume ID, Disk ID, Start Address, TPV ID, Record Access Information, and Segment Size. The volume information203provides Type (i.e., conventional or TPV), Size, and public Volume ID for each volume. This volume ID is used to identify the volume by other computers including the host computers500while the conventional volume ID and TPV ID are internal IDs basically. Because the volume information203has volume size (area size) and location of area in the HDD600(disk ID and start address of the area in the disk) for conventional volumes, the storage controller110can manage and provide conventional volumes by using this information. The volume information203also maintains the relation (mapping) between public volume ID and conventional volume ID.

The volume information203is also used to supply TPVs as data storage volumes provided by the storage system100to the host500, by referring to the TPV ID. In other words, the volume information203maintains the relation (mapping) between the public volume ID and TPV ID. The volume information203also includes information regarding the segment size of each TPV. By referring to options indicated by the segment size information206ofFIG. 2, the segment size is registered by the user via the host500, the management computer520, and/or the management terminal of the storage system100. In addition, the volume information203has the record access information flag which is described later. The initial value of the record access information flag is “Yes.”

C. Overview of Write Process

FIG. 7is an example of a flow diagram illustrating an overview of a process for a write request from the host computer500. At step1001, the host500issues a write request and transfers write data to the storage controller110. At step1002, the storage controller110checks the target volume of the write access by referring to the write request. At step1003, if the type of the target volume is TPV, the storage controller110performs a write process for TPV (step1004). Otherwise, the storage controller110performs a write process for conventional volume (step1005). Each type of the write processes is described in detail below.

D. Overview of Read Process

FIG. 8is an example of a flow diagram illustrating an overview of a process for a read request from host computer500. At step1101, the host500issues a read request and transfers it to the storage controller110. At step1102, the storage controller110checks the target volume of the read access by referring to the read request. At step1103, if the type of the target volume is TPV, the storage controller110performs a read process for TPV (step1104). Otherwise, the storage controller110performs a read process for conventional volume (step1105). Each type of the read processes is described in detail below.

E. Write Process for TPV

FIG. 9is an example of a flow diagram illustrating a write process for TPV610. At step1201, the storage controller110checks the target TPV610and the target area of the write access by referring to the write request. At step1202, the storage controller110checks the mapping information201for a segment in the target area. If a chunk has already been assigned to the segment, the process proceeds to step1205. If not, the process proceeds to step1203. At step1203, the storage controller110assigns a new chunk to store the write data. To do this, the storage controller110updates the mapping information201and pool information202. By using the pool information202, the storage controller110finds the new chunk from the pool volumes620. At step1204, the storage controller110stores the write data to the new chunk. Then the process proceeds from step1204to step1206. At step1205, the storage controller110stores the write data to the existing chunk. The process also proceeds to step1206from step1205. At step1206, the storage controller110updates the access information204and used area information205. At step1207, if the storage controller110has checked all segments of the target area, the process ends. If not, the storage controller110advances the check to the next segment (step1208).

When the storage controller110allocates a chunk for storing the write data, it selects a continuous physical area for the chunk; otherwise, the storage controller110would have to interpret the beginning of the heading, thereby delaying the access speed. This explains why it is generally not effective to simply allocate different numbers of chunks (which typically will not constitute a continuous physical area) to a page instead of changing the size of the chunk (which will be a continuous physical area).

FIG. 10illustrates an example of the access information204in the form of a table. The table presents columns of TPV ID, Read/Write, Access rate per unit time, Average access length, and Frequency of transcending segment boundary (e.g., 1 MB boundary increasing incrementally to 128 MB boundary). The access information204maintains information regarding access characteristics including the frequency of transcending segment boundary in per unit time for various segment sizes as well as access rate per unit time and average access length for each of read and write. The assumed segment size for recording transcending boundary is supposedly based on the segment size information206. The information regarding the average access length may be initialized at a certain interval.

FIG. 11andFIG. 12illustrate examples of the used area information205. The used area information205maintains information to identify used area and unused area. In the example shown inFIG. 11, the area in the TPV is divided by the minimum segment size (e.g., 1 MB) indicated by the segment size information206regardless of the actual segment size and occurrence of access for each “minimum segment” is recorded. In the example, “Yes” means occurrence of access (i.e., used area) and “No” means unused area. In the other example shown inFIG. 12, the accessed area (i.e., used area) in bytes is recorded.

F. Read Process for TPV

FIG. 13is an example of a flow diagram illustrating a read process for TPV610. At step1301, the storage controller110checks the target TPV610and the target area of the read access by referring to the read request. At step1302, the storage controller110checks the mapping information201for a segment in the target area. If a chunk has already been assigned to the segment, the process proceeds to step1303. If not, the process proceeds to step1305. At step1303, the storage controller110transfers data stored in the chunk to the host500. At step1304, the storage controller110updates the access information204and the used area information205. At step1305, the storage controller110sends data of zero (0) to the host500. After step1304or step1305, at step1306, if the storage controller110has checked all segments of the target area, the process ends. If not, the storage controller110advances the check to the next segment (step1307).

G. Write Process for Conventional Volume

With this invention, the access information204and used area information205are recorded (i.e., the access characteristics are monitored) also for the conventional volumes630if the flag of the record access information in the volume information203is “Yes.” This flag may be set and changed for conventional volume630by the user via the host500, management computer520, and/or management terminal of the storage system100. The default value of this flag is “Yes.”

FIG. 14is an example of a flow diagram illustrating a write process for conventional volume630. At step1401, the storage controller110checks the target conventional volume630and the target area of the write access by referring to the write request. At step1402, the storage controller110stores the write data to the target area of the write access. At step1403and step1404, the storage controller110checks the record access information flag in the volume information203. If the flag is “Yes,” the process proceeds to step1405. If not, the process ends. At step1405, the storage controller110updates the access information204and used area information205.

The access information204and used area information205for conventional volume are the same as access information204and used area information205for TPV except for having conventional volume ID instead of TPV ID.

H. Read Process for Conventional Volume

FIG. 15is an example of a flow diagram illustrating a read process for conventional volume630. At step1501, the storage controller110checks the target conventional volume630and the target area of the read access by referring to the read request. At step1502, the storage controller110transfers data stored in the target area of the read access to the host500. At step1503, the storage controller110checks the record access information flag in the volume information203. At step1504, if the flag is “Yes,” the process proceeds to step1505. If not, the process ends. At step1505, the storage controller110updates the access information204and used area information205.

I. Chunk Size Decision Process

FIG. 16is an example of a flow diagram illustrating a procedure to determine chunk size. As described above, at the first step (step1601), the storage controller110monitors accesses for a volume by maintaining and updating the access information204and used area information205. At step1602, based on the monitoring data, the storage controller110analyzes the effectiveness of each option of chunk size. The analysis is achieved based on the monitoring data maintained by the access information204and used area information205. For example, the storage controller110evaluates the expected performance with estimation of frequency and overhead of solving relation between virtual area and physical area. The storage controller110calculates the overhead based on the access information204including the frequency of transcending segment boundary for each segment size. The storage controller110also evaluates the expected area usage efficiency in case of each segment size by using the used area information205. At step1603, the storage controller110makes a report regarding the evaluation mentioned above. At step1604, the report is transferred and presented to a user via the management computer520. At step1605, the user judges the necessity for applying a new chunk size. At step1606, if the user prefers to apply a new chunk size, the process proceeds to step1607. Otherwise, the process proceeds to the next evaluation/decision cycle (step1601). The next cycle is performed with the updated monitoring data (i.e., access information204and used area information205). At step1607, according to the presented evaluation, the user selects the chunk size to be applied. At step1608, the user instructs to apply the new (selected) chunk size of the volume to the storage controller110via the management computer520. The management computer520issues an instruction to apply the new chunk size to the storage controller110. At step1609, the storage controller110receives the instruction from the management computer520and the storage controller110applies the specified chunk size to the volume according to the instruction. Some examples of the process to apply the chunk size or change chunk size to the specified chunk size are described below.

In the above example of the process, the report is presented and the instruction is processed via the management computer520. However, as another example, these steps may be performed between the user and the storage controller110directly.

Regarding execution of the estimation, as another example, the access information204and used area information205can be transferred to the management computer520and the analysis of the access information204and the used area information205may be performed by the management computer520to provide the estimation.

J. Applying New Chunk Size

FIG. 17andFIG. 20show examples of a flow diagram illustrating a process to apply a new chunk size mentioned above. In the example shown inFIG. 17, the changing relation denoted by the mapping information201is utilized to apply the new chunk size. At step1701, the storage controller110checks the TPV610specified by the received instruction for changing the chunk size. At step1702, the storage controller110checks the mapping information201. If there are one or more chunks to be copied between chunks of different sizes to accomplish changing the chunk size, the process proceeds to step1703. Otherwise, the process ends. At step1703, the storage controller110secures one or more new chunks of the specified size by referring to and updating the pool information202. At step1704, the storage controller110copies data in the current (old) chunks to the new chunks according to the used area information205. At step1705, the storage controller110updates the mapping information201to change relation between the TPV610and chunks. That is, the storage controller110replaces the old chunks with the new chunks in the TPV610. At step1706, the storage controller110updates the pool information202to release the old chunks. Then the process returns to step1702.

With the above process, the new chunk size is applied to the TPV610and the same TPV ID (and volume ID) is used continuously before and after this process.

FIG. 18andFIG. 19show examples of segment (chunk) relation between before and after the above process of applying a new chunk size ofFIG. 17. As shown in these figures, data in one chunk may be copied to multiple new chunks and data in multiple chunks may be copied to one new chunk. In addition, copying data in multiple chunks to multiple new chunks is also possible.

In the example shown inFIG. 20of a process to apply a new chunk size, a new TPV610having a specified segment (chunk) size is used to apply the chunk size, and the volume relation denoted by the volume information203is changed to utilize the same volume ID continuously before and after the process. At step1801, the storage controller110obtains a new TPV610having a chunk size specified in the aforesaid instruction. At step1802, the storage controller110reads data from the volume specified by the instruction according to the used area information205. That is, only existing data is read from the volume basically. At step1803, the storage controller110writes the data to the new TPV610with maintaining correspondence. In this write process, chunks of the designated size are utilized. At step1804, the storage controller110updates the volume information203to change the relation between the volume ID and the volumes. That is, the storage controller110replaces the current (old) volumes with the new TPV610. At step1805, the storage controller110checks whether the old volume is a conventional volume630or a TPV610. If the volume is TPV, the process proceeds to step1806. If the volume is conventional volume, the process ends. At step1806, the storage controller110releases the old volume (old TPV) by updating the mapping information201and pool information202.

The above process can be used for conversion from a conventional volume to a TPV having the specified segment (chunk) size as well as conversion between TPVs.

In addition to the above examples of a process to apply a new chunk size, as another example, the host500or management computer520can read data from the specified volume and write the data to a TPV having the designated segment (chunk) size.

K. Another Example of Chunk Size Decision Process

FIG. 21is another example of a flow diagram illustrating a procedure to determine chunk size. With the process described below, the effectiveness evaluation to choose the appropriate chunk size can be performed immediately without access monitoring in advance. At step1901, the storage controller110initializes the used area information205. At step1902, the agent program504on the host500reads all data stored in the volume to be evaluated. In the read process, the actual location of existing data in the volume is recorded in the used area information205. At step1903, the storage controller110analyzes the effectiveness of each option of chunk size. The analysis is achieved based on the used area information205. The storage controller110can evaluate the expected area usage efficiency in case of each segment size by referring to the used area information205. At step1904, the storage controller110makes a report regarding the evaluation mentioned above. At step1905, the report is transferred and presented to the user via the management computer520. At step1906, the user judges the necessity for applying a new chunk size. At step1907, if the user prefers to apply a new chunk size, the process proceeds to step1908. Otherwise, the process ends. Steps1908,1909, and1910are the same as steps1607,1608, and1609shown inFIG. 16. The above procedure may be conducted by the management program523on the management computer520.

With the method described above, the benefit/effectiveness of adopting a certain chunk size can be evaluated and presented based on the monitoring data of accesses so that it enables users to choose an appropriate chunk size.

In the above description of processes, the monitoring data composed of access information204and used area information205is maintained in tabular form. However, as another example of the processes, the monitoring data of accesses can be one or more logs that record accesses for volumes. The monitoring data can be maintained in the disks600.

Of course, the system configuration illustrated inFIG. 1is purely exemplary of information systems in which the present invention may be implemented, and the invention is not limited to a particular hardware configuration. The computers and storage systems implementing the invention can also have known I/O devices (e.g., CD and DVD drives, floppy disk drives, hard drives, etc.) which can store and read the modules, programs and data structures used to implement the above-described invention. These modules, programs and data structures can be encoded on such computer-readable media. For example, the data structures of the invention can be stored on computer-readable media independently of one or more computer-readable media on which reside the programs used in the invention. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include local area networks, wide area networks, e.g., the Internet, wireless networks, storage area networks, and the like.

In the description, numerous details are set forth for purposes of explanation in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that not all of these specific details are required in order to practice the present invention. It is also noted that the invention may be described as a process, which is usually depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged.

As is known in the art, the operations described above can be performed by hardware, software, or some combination of software and hardware. Various aspects of embodiments of the invention may be implemented using circuits and logic devices (hardware), while other aspects may be implemented using instructions stored on a machine-readable medium (software), which if executed by a processor, would cause the processor to perform a method to carry out embodiments of the invention. Furthermore, some embodiments of the invention may be performed solely in hardware, whereas other embodiments may be performed solely in software. Moreover, the various functions described can be performed in a single unit, or can be spread across a number of components in any number of ways. When performed by software, the methods may be executed by a processor, such as a general purpose computer, based on instructions stored on a computer-readable medium. If desired, the instructions can be stored on the medium in a compressed and/or encrypted format.

From the foregoing, it will be apparent that the invention provides methods, apparatuses and programs stored on computer readable media for determining the unit size of storage area in a storage system that provides thin provisioned volumes, from viewpoints such as area usage efficiency and performance. Additionally, while specific embodiments have been illustrated and described in this specification, those of ordinary skill in the art appreciate that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments disclosed. This disclosure is intended to cover any and all adaptations or variations of the present invention, and it is to be understood that the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with the established doctrines of claim interpretation, along with the full range of equivalents to which such claims are entitled.