Specifications

www.ibm.com/support/techdocs 15

Summary of Best Practices for Storage Area Networks

The above values are for 3.5 inch hard disk drives (HDD), and can be increased by

approximately 15% when using the smaller 2.5 inch HDD. Thus, an eight 15K RPM,

3.5” drive RAID 5 array (7 + P) should be capable of between 1155 to 1400 IOps.

Another generic factor for disk-based storage systems involves separation of

different types of workload over storage system ports. In particular, storage ports

used for the following purposes should be dedicated for each type and not be

shared:

• Data mirroring and replication to another storage system

• SVC cluster

• Direct host access

These three workloads have subtle differences between each other, yet can also

stress a given storage system port severely.

Another generic best practice statement involves “housekeeping”. Whenever an

allocated volume, or LUN, is no longer needed by any server, release the allocated

storage back to the free space pool. The reasoning for this suggestion is to help the

storage administrator more easily and quickly determine the availability of storage

resources on a storage system for other needs. Similarly, delete the host definition

information on the storage system whenever a server has been decommissioned, or

sunset. Many storage systems are limited in the total number of host definitions

within their internal configuration. Removing host definitions will also reduce the risk

of production data corruption in cases where an old production server is repurposed

for testing and/or development use.

4.2 DS8000

A DS8000 array is a RAID 5 or RAID 10 array made up of 8 disk drive modules

(DDM). A DS8000 array is created from one array site. DS8000 RAID 5 arrays will

be composed of array width of 6+P+S or 7+P. A rank is created for each array.

There is a one-to-one relationship between arrays and ranks. SAN Volume

Controller, as part of the open system server can access and use ranks created in

Fixed Block (FB) format. FB format divides ranks into 1 GB Extents.

In the DS8000 architecture, extent pools are used to manage one or several Ranks.

An extent pool is visible to both of the two servers in the DS8000, but is directly

managed by only one of the storage controllers. You must define a minimum of two