Specifications

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Summary of Best Practices for Storage Area Networks

extent pools with a pool to be managed by each storage controller to fully exploit the

DS8000’s resources. There is a minimum of one rank per extent pool.

Although it is possible to configure many ranks in an extent pool, for SAN Volume

Controller performance optimization, best practice guidelines recommend a

configuration of one extent pool per rank per array. This configuration allows for

directing storage allocations to a known location within the DS8000. Furthermore,

this configuration enhances the ability to manage and monitor the resultant logical

disk performance when required.

The DS8000 provides a mechanism to create multiple volumes from a single extent

pool. This is useful when the storage subsystem is directly presenting storage to the

hosts. In a SAN Volume Controller environment, however, where possible, there

should be a one-to-one mapping between extent pools and Volumes. Ensuring that

the extent pools are configured in this way will make the subsequent load

calculations and the managed disk and managed disk group configuration tasks a lot

easier.

Mixing array sizes within a managed disk group in general is not of concern if the

differences are not too significant. Testing has shown no measurable performance

differences between selecting all 6+p and all 7+p arrays verses mixing 6+p and 7+p

arrays and in fact mixing array sizes can actually help balance workload since it

places more data on the ranks that have the extra performance capability provided

by the 8th disk. There is one small exposure here in the case where an insufficient

number of the larger arrays are available to handle access to the higher capacity. In

order to avoid this ensure that the smaller capacity arrays do not represent more

than 50% of the total number of arrays within the managed disk group.

In summary, to make the most of the performance available from the DS8000

storage subsystems and avoid potential I/O problems:

• When using virtualization, ensure that the storage devices are configured to

provide some type of redundancy against hard disk failures (RAID algorithm).

• Create a one-to-one relationship between extent pool and rank.

• Avoid splitting an extent pool into multiple volumes at the DS8000 layer.

Where possible, create a single volume on the entire capacity of the extent

pool.