you entered is not valid, the controller returns a list of valid values. Using a single disk drive for a single request leaves other disk drives available to simultaneously service other requests.
If the logical drive is in an environment where a single user is transferring large units of data (such as multimedia), performance is maximized when a single data transfer request is serviced with a single data stripe. (A data stripe is the segment size that is multiplied by the number of disk drives in the array that are used for data transfers.) In this case, multiple disk drives are used for the same request, but each disk drive is accessed only once.
For optimal performance in a multiuser database or file system storage
environment, set your segment size to minimize the number of disk drives that are required to satisfy a data transfer request.
You do not need to enter a value for the cacheReadPrefetch parameter or the segmentSize parameter. If you do not enter a value, the controller firmware uses the usageHint parameter with fileSystem as the default value. Entering a value for the usageHint parameter and a value for the cacheReadPrefetch parameter or a value for the segmentSize parameter does not cause an error. The value that you enter for the cacheReadPrefetch parameter or the segmentSize parameter takes priority over the value for the usageHint parameter.
Parameters
Parameter Description
array The alphanumeric identifier (including - and _) for a specific array in your storage subsystem.
userLabel The name that you want to give the new logical drive.
Enclose the new logical drive name in double quotation marks (“ ”).
freeCapacityArea The index number of the free space in an existing array that you want to use to create the new logical drive. Free capacity is defined as the free capacity between existing logical drives in a array. For example, a array might have the following areas: logical drive 1, free capacity, logical drive 2, free capacity, logical drive 3, free capacity. To use the free capacity following logical drive 2, you would specify:
freeCapacityArea=2
Run the show array command to determine if the free capacity area exists.
capacity The size of the logical drive that you are adding to the storage subsystem. Size is defined in units of bytes, KB, MB, GB, or TB.
owner The controller that owns the logical drive. Valid controller identifiers are a or b, where a is the controller in slot A, and b is the controller in slot B. If you do not specify an owner, the controller firmware determines the owner.
cacheReadPrefetch The setting to turn on or turn off cache read prefetch. To turn off cache read prefetch, set this parameter to FALSE.
To turn on cache read prefetch, set this parameter to TRUE.
segmentSize The amount of data (in KB) that the controller writes on a single disk drive in a logical drive before writing data on the next disk drive. Valid values are 8, 16, 32, 64, 128, 256, or 512.
usageHint The settings for both the cacheReadPrefetch parameter and the segmentSize parameter to be default values. The default values are based on the typical I/O usage pattern of the application that is using the logical drive. Valid values are fileSystem, dataBase, or multiMedia.
dssPreAllocate The setting to make sure that reserve capacity is allocated for future segment size increases. The default value is TRUE.
securityType The setting to specify the security level when creating the array and all associated logical drives. These settings are valid:
v none—The array and logical drives are not secure.
v capable—The array and logical drives are capable of having security set, but security has not been enabled.
v enabled—The array and logical drives have security enabled.
Notes
You can use any combination of alphanumeric characters, hyphens, and underscores for the names. Names can have a maximum of 30 characters.
The owner parameter defines which controller owns the logical drive. The preferred controller ownership of a logical drive is the controller that currently owns the array.
If you do not specify a capacity using the capacity parameter, all of the available capacity in the free capacity area of the array is used. If you do not specify capacity units, bytes is used as the default value.
Segment Size
The size of a segment determines how many data blocks that the controller writes on a single disk drive in a logical drive before writing data on the next disk drive.
Each data block stores 512 bytes of data. A data block is the smallest unit of storage. The size of a segment determines how many data blocks that it contains.
For example, an 8-KB segment holds 16 data blocks. A 64-KB segment holds 128 data blocks.
When you enter a value for the segment size, the value is checked against the supported values that are provided by the controller at run time. If the value that you entered is not valid, the controller returns a list of valid values. Using a single disk drive for a single request leaves other disk drives available to simultaneously service other requests.
If the logical drive is in an environment where a single user is transferring large units of data (such as multimedia), performance is maximized when a single data transfer request is serviced with a single data stripe. (A data stripe is the segment size that is multiplied by the number of disk drives in the array that are used for data transfers.) In this case, multiple disk drives are used for the same request, but each disk drive is accessed only once.
For optimal performance in a multiuser database or file system storage
environment, set your segment size to minimize the number of disk drives that are required to satisfy a data transfer request.
Cache Read Prefetch
Cache read prefetch lets the controller copy additional data blocks into cache while the controller reads and copies data blocks that are requested by the host from the disk drives into cache. This action increases the chance that a future request for data can be fulfilled from cache. Cache read prefetch is important for multimedia applications that use sequential data transfers. The configuration settings for the storage subsystem that you use determine the number of additional data blocks that the controller reads into cache. Valid values for the cacheReadPrefetch parameter are TRUE or FALSE. You do not need to enter a value for the
cacheReadPrefetchparameter or the segmentSize parameter. If you do not enter a value, the controller firmware uses the usageHint parameter with fileSystem as the default value.
Entering a value for the usageHint parameter and a value for the
cacheReadPrefetchparameter or a value for the segmentSize parameter does not cause an error. The value that you enter for the cacheReadPrefetch parameter or
the segmentSize parameter takes priority over the value for the usageHint parameter.
Security Type
See “Security Type” on page 214 for an explanation of this new parameter.