Comingling conventional and backup volumes in tiered storage systems

A method for efficiently managing extents of backup volumes in a tiered storage system is disclosed. In one embodiment, such a method includes identifying a lifespan associated with a backup volume. The lifespan indicates how long extents of the backup volume are retained in a tiered storage system before being released. The method further assigns a temperature value to the extents that determines where the extents are stored in the tiered storage system. The method utilizes the lifespan to determine the temperature value, where the temperature value is inversely proportional to the lifespan. The method places the extents on tiers of the tiered storage system in accordance with their temperature value, such that higher temperature extents are placed on higher tiers of the tiered storage system, and lower temperature extents are placed on lower tiers of the tiered storage system. A corresponding system and computer program product are also disclosed.

BACKGROUND

Field of the Invention

This invention relates to systems and methods to efficiently manage extents from both CDP backup volumes and conventional volumes in tiered storage systems.

Background of the Invention

Data is often one of an organization's most valuable assets. Accordingly, it is paramount that an organization regularly back up its data, particularly its business-critical data. Statistics show that a high percentage of organizations, as high as fifty percent, are unable to recover from an event of significant data loss, regardless of whether the loss is the result of a virus, data corruption, physical disaster, software or hardware failure, human error, or the like. At the very least, significant data loss can result in lost income, missed business opportunities, and/or substantial legal liability. Accordingly, it is important that an organization implement adequate backup policies and procedures to prevent such losses from occurring.

Various different solutions exist for backing up an organization's data. One solution, referred to as near continuous data protection (CDP), essentially captures every version of data in a backup volume. This enables a user or administrator to restore data to any point-in-time Like conventional data volumes, CDP backup volumes may be made up of extents of fixed size (e.g., 64 MB). However, the extents of CDP backup volumes may differ from those of conventional volumes in some important ways. For example, the extents of CDP backup volumes are typically written with data shortly after they are allocated and then not accessed again for the life of the extents (unless in the rare case they are used for recovery purposes). After their lifespans have passed, the extents may be released.

Due to the differences between CDP backup volumes and conventional volumes, challenges may arise when storing the volumes together in tiered storage systems. In such systems, extents of data are migrated between tiers of differing I/O performance based on the hotness/coldness of the data contained therein. When storing CDP backup volumes and conventional volumes in tiered storage systems, issues arise such as where (i.e. on which tiers) to allocate the extents of each type of volume, as well as when and whether to migrate the extents between the tiers.

In view of the foregoing, what are needed are systems and methods to efficiently manage extents from both CDP backup volumes and conventional volumes in tiered storage systems.

SUMMARY

The invention has been developed in response to the present state of the art and, in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available systems and methods. Accordingly, systems and methods are disclosed to efficiently manage extents of continuous data protection (CDP) backup volumes and conventional volumes in a tiered storage system. The features and advantages of the invention will become more fully apparent from the following description and appended claims, or may be learned by practice of the invention as set forth hereinafter.

Consistent with the foregoing, a method for efficiently managing extents of backup volumes in a tiered storage system is disclosed. In one embodiment, such a method includes identifying a lifespan associated with a backup volume. The lifespan indicates how long extents of the backup volume are retained in a tiered storage system before being released. The method further assigns a temperature value to the extents that determines where the extents are stored in the tiered storage system. The method utilizes the lifespan to determine the temperature value, where the temperature value is inversely proportional to the lifespan. The method places the extents on tiers of the tiered storage system in accordance with their temperature value, such that higher temperature extents are placed on higher tiers of the tiered storage system, and lower temperature extents are placed on lower tiers of the tiered storage system.

A corresponding system and computer program product are also disclosed and claimed herein.

DETAILED DESCRIPTION

The present invention may be embodied as a system, method, and/or 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 program instructions may execute entirely on a user's computer, partly on a user's computer, as a stand-alone software package, partly on a user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter scenario, a remote computer may be connected to a 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.

Referring toFIG. 1, one example of a network environment100is illustrated. The network environment100is presented to show one example of an environment where systems and methods in accordance with the invention may be implemented. The network environment100is presented by way of example and not limitation. Indeed, the systems and methods disclosed herein may be applicable to a wide variety of network environments, in addition to the network environment100shown.

As shown, the network environment100includes one or more computers102,106interconnected by a network104. The network104may include, for example, a local-area-network (LAN)104, a wide-area-network (WAN)104, the Internet104, an intranet104, or the like. In certain embodiments, the computers102,106may include both client computers102and server computers106(also referred to herein as “host systems”106). In general, the client computers102initiate communication sessions, whereas the server computers106wait for requests from the client computers102. In certain embodiments, the computers102and/or servers106may connect to one or more internal or external direct-attached storage systems112(e.g., arrays of hard-disk drives, solid-state drives, tape drives, etc.). These computers102,106and direct-attached storage systems112may communicate using protocols such as ATA, SATA, SCSI, SAS, Fibre Channel, or the like.

The network environment100may, in certain embodiments, include a storage network108behind the servers106, such as a storage-area-network (SAN)108or a LAN108(e.g., when using network-attached storage). This network108may connect the servers106to one or more storage systems110, such as arrays110aof hard-disk drives or solid-state drives, tape libraries110b, individual hard-disk drives110cor solid-state drives110c, tape drives110d, CD-ROM libraries, or the like. To access a storage system110, a host system106may communicate over physical connections from one or more ports on the host106to one or more ports on the storage system110. A connection may be through a switch, fabric, direct connection, or the like. In certain embodiments, the servers106and storage systems110may communicate using a networking standard such as Fibre Channel (FC).

Referring toFIG. 2, one embodiment of a storage system110acontaining an array of hard-disk drives204and/or solid-state drives204is illustrated. The internal components of the storage system110aare shown since certain functionality in accordance with the invention may be implemented within such a storage system110a. As shown, the storage system110aincludes a storage controller200, one or more switches202, and one or more storage drives204, such as hard disk drives204or solid-state drives204(such as flash-memory-based drives204). The storage controller200may enable one or more hosts106(e.g., open system and/or mainframe servers106) to access data in the one or more storage drives204.

In selected embodiments, the storage controller200includes one or more servers206. The storage controller200may also include host adapters208and device adapters210to connect the storage controller200to host devices106and storage drives204, respectively. Multiple servers206a,206bmay provide redundancy to ensure that data is always available to connected hosts106. Thus, when one server206afails, the other server206bmay pick up the I/O load of the failed server206ato ensure that I/O is able to continue between the hosts106and the storage drives204. This process may be referred to as a “failover.”

In selected embodiments, each server206may include one or more processors212and memory214. The memory214may include volatile memory (e.g., RAM) as well as non-volatile memory (e.g., ROM, EPROM, EEPROM, hard disks, flash memory, etc.). The volatile and non-volatile memory may, in certain embodiments, store software modules that run on the processor(s)212and are used to access data in the storage drives204. These software modules may manage all read and write requests to logical volumes in the storage drives204.

One example of a storage system110ahaving an architecture similar to that illustrated inFIG. 2is the IBM DS8000™ enterprise storage system. The DS8000™ is a high-performance, high-capacity storage controller providing disk storage that is designed to support continuous operations. Nevertheless, the systems and methods disclosed herein are not limited to the IBM DS8000™ enterprise storage system110a, but may be implemented in any comparable or analogous storage system110, regardless of the manufacturer, product name, or components or component names associated with the system110. Furthermore, any storage system that could benefit from one or more embodiments of the invention is deemed to fall within the scope of the invention. Thus, the IBM DS8000™ is presented only by way of example and is not intended to be limiting.

Referring toFIG. 3, in certain embodiments, one or more storage systems110such as that illustrated inFIG. 2may be configured to provide tiered data storage. In such an environment, the “hotness” or “coldness” of data may be continually monitored so that it can be optimally placed on different storage tiers300. For example, faster storage drives204a(e.g., higher performance solid state drives) may make up a first storage tier300a, intermediate performance storage drives204b(e.g., lower performance solid state drives, higher performance hard-disk drives, etc.) may make up a second storage tier300b, while slower storage drives204c(e.g., lower performance hard-disk drives) may make up a third storage tier300c. “Hot” (i.e., frequently accessed) data may be placed on the first storage tier300ato improve I/O performance, while “warm” (i.e., less frequently accessed) data may be placed on the second storage tier300b. “Cold” (i.e., even less frequently accessed) data may be placed on the third storage tier300c. As the temperature of the data changes, the data may be migrated between the storage tiers300a-cto optimize I/O performance. The storage tiers300a-cmay be implemented within a single storage system110or potentially distributed across multiple storage systems110. Similarly, additional (or fewer) tiers300may be provided where needed. The example described above is provided only by way of example and not limitation.

Referring toFIG. 4, as previously mentioned, various different solutions may be used to back up an organization's data. One solution, referred to as near continuous data protection (CDP), essentially captures every version of data in a backup volume412b. This enables a user or administrator to restore data to any point-in-time. Like conventional data volumes412a, CDP backup volumes412bmay be made up of extents414bof fixed size (e.g., 64 MB). However, the extents414bof CDP backup volumes412bmay differ from the extents414aof conventional volumes412ain some important ways. For example, the extents414bof CDP backup volumes412bmay be written with data shortly after they are allocated and then not be accessed again for the life of the extents414b(unless in the rare case they are used for recovery purposes).

After their designated lifespans have passed, the extents414bof the CDP backup volumes412bmay be released. Because CDP backup volumes412band conventional volumes412ahave different access characteristics, challenges arise when trying to store the volumes412a,412btogether in tiered storage systems302. In such systems302, extents414are migrated between tiers300based on the hotness/coldness of data therein. When storing CDP backup volumes412band conventional volumes412ain tiered storage systems302, questions arise such as to where (i.e. on which tiers300) to allocate the extents414of each of these types of volumes412, as well as when and whether to migrate the extents414between the tiers300of the tiered storage system302.

In order to efficiently manage extents414from both CDP backup volumes412band conventional volumes412ain tiered storage systems302, a backup extent management module400may be implemented within the storage controller200. The backup extent management module400may be implemented in software, hardware, firmware, or a combination thereof. The backup extent management module400may include various sub-modules402-410to perform various features and functions. For example, as shown, the backup extent management module400may include one or more of a lifespan determination module402, temperature determination module404, allocation module406, migration module408, and release module410. These sub-modules are provided by way of example and not limitation. More or fewer sub-modules may be provided in different embodiments. For example, the functionality of some sub-modules may, in certain embodiments, be combined into a single or smaller number of sub-modules, or the functionality of a single sub-module may be distributed across several sub-modules.

With conventional volumes412a, extents414aare typically migrated between tiers300of a tiered storage system302based on the temperature of data contained therein. As I/O occurs to the extents414a, the temperature of the extents414amay change and the extents414amay be migrated between tiers300accordingly. The extents414bof CDP backup volumes412bare different from those of conventional volumes412ain that the extents414bare typically written to shortly after they are allocated and then are typically not accessed again for the life of the extents. Thus, there is typically heavy I/O to the extents414bright after allocation and then virtually no I/O after the extents414bhave been written with data. The extents414bmay then reside on the storage drives204virtually undisturbed until their lifespans are complete, at which time the extents414bmay be released to free up storage space for new extents414. For the purpose of this disclosure, the “lifespan” of a backup extent414bis the period of time from the moment the extent414bis allocated to the moment it is released.

Because of the different ways that conventional volumes412aand CDP backup volumes412bare accessed, systems and methods are needed to assign a “temperature” to extents414bof CDP backup volumes412bso that the extents414bmay coexist with conventional extents414ain a tiered storage system302. Once temperature is assigned to these backup extents414b, hierarchical storage management (HSM) software in the tiered storage system302may manage and migrate the backup extents414bin much the same way as the extents414aof conventional volumes412a.

In certain embodiments in accordance with the invention, a pseudo “temperature value” may be derived from the lifespan of backup extents414b. Like the temperature value for a conventional extent414a, this temperature value may be used by hierarchical storage management software to properly place and migrate the backup extents414balong with conventional extents414abetween tiers300of a tiered storage system302.

The lifespan determination module402may be configured to identify a lifespan associated with a CDP backup volume412b. In certain embodiments, the lifespan of a CDP backup volume412bis the average of the lifespans of the extents414bin the CDP backup volume412b. In certain embodiments, the lifespan for a CDP backup volume412bis defined by a user. This may be expressed in terms of how many versions of data a user wants to keep, and/or how long the user wants to keep data before it is released or retired. In other cases, the user may specify a capacity limitation for a CDP backup volume412band the lifespan for extents414bwithin this CDP backup volume412bmay depend on this capacity limitation. For example, once a CDP backup volume412bhits its designated capacity limitation, the oldest extent414bin the CDP backup volume412bmay be released to ensure that the CDP backup volume412bdoes not grow beyond its capacity limitation. Thus, the capacity limitation may, in certain embodiments, dictate the lifespan of the extents414btherein.

Bases on the lifespan of a CDP backup volume412b, the temperature determination module404may calculate a temperature value for a backup extent414bcontained therein. In certain embodiments, the temperature value is represented in terms of data writes per day (DWPD) divided by the lifespan in days. The DWPM may designate how many times the entire capacity of the extent414bis overwritten per day. For example, for a 10 GB allocation of storage space in a CDP backup volume412bwith a lifespan of ten days, the only workload to the storage space during the ten day lifespan is the initial 10 GB write. Translating this to DWPD, the storage space will be overwritten in its entirely once in ten days, so the DWPD is 1/10, or 0.1 DWPD. In general, the workload for the CDP backup volume412bwill be a pure write workload of N DWPD, where N is the reciprocal of the lifespan in days. In general, a longer lifespan will result in a lower DWPD and vice versa.

In general, there is no difference among extents414bof the same CDP backup volume412bfrom the workload's perspective. Thus, no special consideration or treatment may be given to extents414in the same CDP backup volume412b. Each extent414bin the CDP backup volume412bmay be considered to have the same lifespan and thus the same temperature value. However, different CDP backup volumes412bmay have different lifespans. Consider the case of a CDP backup volume412bthat has a very short lifespan of one hour. In such a case, the workload for the CDP backup volume412bis 24 DWPD which is quite hot and not a good candidate for storage on large capacity flash storage drives204(which may be optimized for 1 to 3 DWPD, for example). Consider a contrasting case where a CDP backup volume412bhas a lifespan of one month. In such a case, the workload is 0.03 DWPD which is quite cold and not a good candidate for storage on high performance flash storage drives204(optimized for 10 DWPD). In either case, the extents414bof the CDP backup volumes412bmay be placed on tiers300of the tiered storage system302in accordance with their temperature.

When data is written to a CDP backup volume412b, the allocation module406may allocate extents414with the temperature value of the CDP backup volume412bto accommodate the data. In certain embodiments, these backup extents414bmay initially be allocated on the highest tier300aregardless of their temperature since this will provide the highest level of I/O performance while data is being written thereto. The migration module408may then migrate the backup extents414bbetween tiers300in accordance with their temperature value. This may include leaving the backup extents414bon the highest tier300aor moving the backup extents414bto lower tiers300b,300cdepending on their temperature. After the lifespan of a backup extent414bis complete, the release module410may release the backup extent414b, thereby freeing up storage space for use by other extents414. As previously mentioned, the lifespan may be a fixed time period designated by a user, or vary based on a capacity limitation and/or workload of a CDP backup volume412b.

Referring toFIG. 5, using systems and methods in accordance with the invention, extents414a,414bfrom both conventional volumes412aand backup volumes412bmay be comingled on tiers300of a tiered storage system302. In certain embodiments, the temperature values for conventional extents414aare based on data accesses per day (DAPD), which may be the sum of data writes per day and data reads per day. For backup extents414b, the DAPD may be equal to the DWPD previously discussed. Once the temperature values for conventional extents414aand backup extents414bare known, the extents414may be sorted and placed on appropriate tiers300of the tiered storage system302. Extents414with higher temperature values may be placed on higher performance tiers300and extents414with lower temperature values may be placed on lower performance tiers300.

The temperature values assigned to backup extents414bmay enable the backup extents414bto be migrated between tiers300just like extents414aof conventional volumes412a, with some exceptions. In certain embodiments, new backup extents414bmay be allocated on the first tier300a, thereby enabling data to be quickly written thereto. These new backup extents414bmay then be migrated to other storage tiers300b,300cif warranted by their temperature values. For example, if a backup extent414bis cold, the backup extent414bmay be migrated from the first tier300ato the third tier300c, as shown inFIG. 5. On the other hand, unlike conventional extents414a, once on a lower performance tier300, backup extents414bmay not be migrated to higher storage tiers300regardless of their temperature values, as shown inFIG. 5. This is because there may be no benefit to move backup extents414bto higher tiers300since there is normally no I/O to the backup extents414b. Thus, once on lower performance storage tiers300, backup extents414bmay remain on the lower storage tiers300until they are released.

Referring toFIG. 6, one embodiment of a method600for handling I/O in a tiered storage system302that commingles extents414of conventional volumes412aand backup volumes412bis illustrated. As shown, upon receiving an I/O request at step602, the method600determines604whether the I/O request is directed to a CDP backup volume412b. If not, the I/O request is directed to a conventional volume412a. In such case, the method600adjusts606a temperature of the conventional extent414ato reflect the I/O and the method600executes614the I/O.

If, on the other hand, the I/O request is associated with a CDP backup volume412b, the method600determines608whether an extent414bhas been allocated to receive the I/O request. If so, the method600executes614the I/O request on the already allocated extent414b. If an extent414bhas not already been allocated, the method600allocates610a backup extent414bwith the temperature value of the CDP backup volume412bthat it belongs to. The method600also records612the allocation time of the extent414b. The method600then executes614the I/O request on the newly allocated extent414b.

Referring toFIG. 7, one embodiment a method700that is executed when releasing an extent414a, is illustrated. As shown, the method700initially determines702whether an extent414is to be released. If so, the method700determines704whether the extent414is associated with a CDP backup volume412b. If not, the extent414ais associated with a conventional volume412a. In such case, the method700resets706the temperature associated with the extent414aand releases714the extent414ato free storage space associated therewith.

If, on the other hand, the extent414being released belongs to a CDP backup volume412b, the method700fetches708the allocation time associated with the extent414band calculates the lifespan of the extent414b. This may be accomplished by determining the time between the allocation time the release time. Once the lifespan of the extent414bis determined710, the method700may update712the lifespan of the CDP backup volume412bthat is used to calculate the temperature value for the CDP backup volume412b. In certain embodiments, the lifespan of the CDP backup volume412bis the average of the lifespans for extents414bin the CDP backup volume412b. Thus, the lifespan of the extent414bbeing released may be factored into the lifespan of the CDP backup volume412b. In cases where the lifespans of extents414in a CDP backup volume412bare static, such as in cases where a user designates a fixed time period to retain extents414b, the lifespan of the CDP backup volume412bwill also be static. After the method700updates the lifespan of the CDP backup volume412b(if needed), the method700releases714the extent414bto free storage space associated therewith.