IBM System Storage DS3000 Programming Manual page 425

self-adjusting based on the rate and request size of the host reads. Random access does not cause data to
be pre-fetched into cache. This feature has no effect when read caching is disabled.
Note:
v When you are creating a thin logical drive, the dynamic cache read prefetch option is not available.
v Regardless of the capacity specified, capacity in a disk pool is allocated in 4 GB increments. Any
capacity that is not a multiple of 4 GB is allocated, however not usable. To make sure that the entire
capacity is usable, specify the capacity in 4 GB increments. If unusable capacity exists, the only way to
regain it is to increase the capacity of the logical drive.
Creating standard logical drives on a disk pool
If you want to add a new standard logical drive to an existing disk pool, use this command:
create logicalDrive diskPool="diskPoolName"
userLabel="logicalDriveName"
capacity=logicalDriveCapacity
thinProvisioned=FALSE |
[owner=(a|b) |
mapping=(none|default) |
T10PI=(none|enabled) |
cacheReadPrefetch=(TRUE | FALSE)]
The diskPool parameter is the name of the disk pool in which you want to create a new logical drive. If
you do not know the disk pool names on the storage subsystem, you can use the show storageSubsystem
summary command to get a list of the disk pool.
The userLabel parameter is the name that you want to give to the logical drive. The logical drive name
can be any combination of alphanumeric characters, hyphens, and underscores. The maximum length of
the logical drive name is 30 characters. You must enclose the logical drive name with double quotation
marks (" ").
The capacity parameter defines the capacity to use for the logical drive.
The thinProvisioned parameter sets the logical drive to either standard or thin. For a standard logical
drive, the thinProvisioned parameter must be set to FALSE.
The owner parameter defines which controller is designated to be the primary controller of the logical
drive. For best performance ensure that the controllers are balanced as closely as possible for total I/Os.
The mapping parameter defines whether you want the storage management software to map the logical
drive to a host, or if you want to map the logical drive to a host at a later time. To allow the storage
management software to map the logical drive to a host use the default parameter. To map the logical
drive to a host at a later time, use the none parameter. To map a logical drive to a host, use the set
logicalDrive logicalUnitNumber command.
To turn on T10PI, set the T10PI parameter to enabled.
To turn on cache read prefetch, set the cacheReadPrefect parameter to TRUE.
The usage of the owner parameter, the cacheReadPrefetch parameter, and the segmentSize parameter is
the same as described in the previous examples of the create logicalDrive command.
Creating thin logical drives on a disk pool
If you want to add a new thin logical drive to an existing disk pool, use this command:
create logicalDrive diskPool="diskPoolName"
userLabel="logicalDriveName" capacity=logicalDriveVirtualCapacity
thinProvisioned=TRUE
Chapter 4. Configuring a Storage Subsystem
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