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IBM DS8880 Provides New Flexibility for Storage Growth, Efficiency and Resilience

IBM DS8880

The IBM DS8000 series of storage systems are essential to helping IT leaders get the most value from their mainframe assets. The latest model family, IBM DS8880, provides better management for the changing conditions in the modern enterprise including the dynamic demands of cloud, mobile, social and analytics strategies. The DS8880 V8.1.1 firmware enhancements provide new capabilities such as thin provisioning that further extends the cost effectiveness of mainframe owned and managed data.

The IBM DS8880 thin provisioning support became available in July, with the version 8.1.1 firmware release and corresponding software exploitation Small Programming Enhancement (SPE) for z/OS V2.1 and above (APARs PI47180, OA48710, OA48723, OA48711, OA48709, OA48707 and OA50453).

Complementing the thin provisioning capability, the DS8880 provides Super Parallel access volumes (IBM DS8000 SuperPAV) to provide additional I/O capacity transparently to the systems programmers, storage administrators and database administrators. Improved resilience is provided against bursts of new work driven by mobile users or after various potential hardware failures in the infrastructure by the potential improved I/O rates possible. The IBM DS8000 SuperPAV technology became available July with the DS8880 V8.1 firmware release and corresponding software exploitation SPE for z/OS V2.1 and above (APARs OA49090, OA49110 and OA49415).

Finally, IBM introduced the DB2 Cast Out Accelerator, a new storage technology for accelerating DB2 cast out processing that’s critical for resilience. The IBM DS8000 DB2 Cast Out Accelerator became available in June with the DS8880 V8.1 firmware release and corresponding software exploitation SPE for z/OS V2.1 and above (APAR OA49684). The new function is transparent to DB2 and therefore exploited by all releases of DB2.

Thin Provisioning for the Mainframe

The DS8000 uses a virtualization layer to abstract the creation of volumes from the underlying storage. This layer creates regular sized chunks of data called extents on the RAID arrays and then creates storage pools of these extents which can be used for volume creation. Storage pool striping, Easy Tier and thin provisioning exploit this to provide their function. Prior to DS8000 V8.1, the extent size was fixed at 1113 cylinders for mainframe (ECKD) volumes and 1 GB for fixed block volumes. DS8880 firmware release level 8.1 introduces the capability to optionally define a storage pool as using small extents which are 21 cylinders, or 16 MB, in size.

Small extents provide a number of benefits:

  • The striping of data over RAID arrays in a pool is now at a much more granular level so the workload distribution will be better even over very short time periods. With the larger extents, a burst of read or write activity could last for 20 to 30 seconds, which could be concentrated on a single 1113-cylinder extent. The same burst of activity with small extents is likely to be spread over most of the RAID arrays in the pool to avoid even a brief hotspot on one of the arrays.
  • Easy Tier will also see efficiency improvements, especially in thin provisioned environments. With small extents, statistics are not collected for each of the small extents, but continue to be collected to do this for groups of extents equal to the large extent size. The exception to this is that the idle extents with no workload are tracked and treated separately from other extents in the group.
  • Thin provisioning is now significantly more efficient from a capacity perspective as the allocation unit for thin provisioning is now 53 times smaller for ECKD and 64x smaller for FB volumes. One of the key reasons for moving to a smaller extent size was to enable the use of thin provisioning for ECKD volumes and the 21-cylinder extent size was chosen to match the dataset allocation unit for Extended Addressability Volumes (EAVs), which can be 1 TB.
  • FlashCopy can also be performed to a thin provisioned device with small extents, providing an improved performance space efficient FlashCopy compared to the previous track space efficient FlashCopy which had significantly lower performance for sequential write workloads. This can also be used for journal volumes in a Global Mirror environment to reduce the capacity requirements for this copy of data.

Nick Clayton is an Executive IT Specialist and Solution Architect for DS8000 development, IBM Systems

Scott B. Compton is a Senior Technical Staff Member and team leader for new device architecture in z/OS development.

Harry M. Yudenfriend is an IBM Fellow with Systems and Technology Group, System z and Power who joined IBM in 1980. He was named an IBM Master Inventor in 2001 and has achieved his 33rd invention plateau.

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