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.
Parameter Description
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 cachReadPrefetch 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.
enclosureLossProtect The setting to enforce enclosure loss protection when you create the repository. To enforce enclosure loss protection, set this parameter to TRUE. The default value is FALSE.
dssPreAllocate The setting to make sure that reserve capacity is allocated for future segment size increases. This 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
If you set the raidLevel parameter to RAID 1, the controller firmware takes the list of drives and pairs them by using this algorithm:
Data drive = X
Parity drive = N/2 + X
In this algorithm X is 1 to N/2, and N is the number of drives in the list. For example, if you have six drives, the mirror pairs are as follows:
Data Parity
1 N/2 + 1 = 4
2 N/2 + 2 = 5
3 N/2 + 3 = 6
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 disk drive capacity that is available in 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 drive 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 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.
For enclosure loss protection to work, each disk drive in a array must be on a separate enclosure. If you set the enclosureLossProtect parameter to TRUE and have selected more than one disk drive from any one enclosure, the storage
subsystem returns an error. If you set the enclosureLossProtect parameter to FALSE, the storage subsystem performs operations, but the array that you create might not have enclosure loss protection. enclosure loss protection is not valid when you create logical drives on existing arrays.
Security Type
See “Security Type” on page 214 for an explanation of this parameter.