IBM DS6000 Series Define migration objectives in z/OS environments, Consolidate logical volumes

13.1 Define migration objectives in z/OS environments

Data migration is an important activity that needs to be planned well to ensure the success of DS6000 implementation. Because today’s business environment does not allow you to interrupt data processing services, it is crucial to make the data migration onto the new storage servers as smooth as possible. The configuration changes and the actual data migration ought to be transparent to the users and applications, with no or only minimal impact on data availability. This requires you to plan for non-disruptive migration methods and to guarantee data integrity at any time.

13.1.1 Consolidate storage subsystems

In the course of a data migration you might consider consolidating the volume environment from which you are coming.

ESCON
	FICON
ESS E20
ESCON	Consolidate
	DS 6000
ESS F20	Not drawn to scale

Figure 13-1 Consolidation opportunities when migrating to DS6000

A DS6800 can contain up to 32 logical control units (LCUs) at GA. This allows the DS6800 to simulate up to 32 times an IBM 3390-6 control unit image with 256 devices within each single control unit image. The number of supported volumes within a DS6800 is 32 x 256 devices which equals 8,192 logical volumes. This is twice as much as what an ESS 2105 can configure for a z/OS-based configuration. This suggests consolidation of multiple control units into a single DS6800 disk storage server. This requires careful planning, and depending on the configuration complexity, it might take weeks or months to complete the planning and perform the actual migration.

13.1.2 Consolidate logical volumes

Another aspect of consolidation within a data migration effort might be to plan for larger volume sizes and consolidate or fold more than one source volume to a new and bigger target volume. Up to now most customers have relied on a standard sized volume, that being an IBM 3390-3 with 3,339 cylinders. With the affinity of volumes to RAID arrays and the underlying 8-packs, the increasing DDM size in the ESS 2105 made it impossible to utilize the full RAID array capacity of a RAID rank with 146 GB and even larger DDMs, when choosing 3390-3 volumes. The full RAID array capacity could only be utilized when changing to bigger volume sizes to reduce the number of volumes per RAID array or LSS. This is not necessary any more with the DS6800 model due to its flexibility to configure its backend storage independently from DDM sizes. There is no affinity any longer between an LSS and physical

252DS6000 Series: Concepts and Architecture