Set Logical Drive

This command defines the properties for a logical drive. You can use most parameters to define properties for one or more logical drives. You also can use some parameters to define properties for only one logical drive. The syntax definitions are separated to show which parameters apply to several logical drives and which apply to only one logical drive. Also, the syntax for logical drive mapping is listed separately.

Syntax Applicable to One or More Logical Drives

set (allLogicalDrives | logicalDrive [“logicalDriveName”] | logicalDrives [“logicalDriveName1” ... “logicalDriveNameN”] | logicalDrive <wwID>) cacheFlushModifier=cacheFlushModifierValue cacheWithoutBatteryEnabled=(TRUE | FALSE) mediaScanEnabled=(TRUE | FALSE) mirrorCacheEnabled=(TRUE | FALSE) modificationPriority=(highest | high | medium | low | lowest) owner=(a | b) readCacheEnabled=(TRUE | FALSE) writeCacheEnabled=(TRUE | FALSE) cacheReadPrefetch=(TRUE | FALSE)

Syntax Applicable to Only One Logical Drive

set (logicalDrive [“logicalDriveName”] | logicalDrive <wwID>) addCapacity=logicalDriveCapacity [addDrives=(enclosureID1,slotID1 ... enclosureIDn,slotIDn)] redundancyCheckEnabled=(TRUE | FALSE) segmentSize=segmentSizeValue userLabel=logicalDriveName preReadRedundancyCheck=(TRUE | FALSE)

Syntax Applicable to Logical Drive Mapping

set (logicalDrive=[“logicalDriveName”] | logicalDrive <wwID> | accessLogicalDrive) logicalUnitNumber=LUN (host=”hostName” | hostGroup=(“hostGroupName” | defaultGroup)

Parameters
Parameter Description
allLogicalDrives The properties for all logical drives in the storage subsystem.
logicalDrive or logicalDrives The name of the specific logical drive for which you want to define properties. (You can enter more than one logical drive name if you use the logicalDrives parameter). Enclose the logical drive name in double quotation marks (“ ”) inside of square brackets ([ ]).
logicalDrive The World Wide Identifier (WWID) of the logical drive for which you are setting properties. You can use the WWID instead of the logical drive name to identify the logical drive. Enclose the WWID in angle brackets (< >).
cacheFlushModifier The maximum amount of time that data for the logical drive stays in cache before the data is flushed to physical storage. Valid values are listed in the Notes section.
cacheWithoutBatteryEnabled The setting to turn on or turn off caching without batteries. To turn on caching without batteries, set this parameter to TRUE. To turn off caching without batteries, set this parameter to FALSE.
mediaScanEnabled The setting to turn on or turn off media scan for the logical drive. To turn on media scan, set this parameter to TRUE. To turn off media scan, set this parameter to FALSE. (If media scan is disabled at the storage subsystem level, this parameter has no effect.)
mirrorCacheEnabled The setting to turn on or turn off the mirror cache. To turn on the mirror cache, set this parameter to TRUE. To turn off the mirror cache, set this parameter to FALSE.
modificationPriority The priority for logical drive modifications while the storage subsystem is operational. Valid values are highest, high, medium, low, or lowest.
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. Use this parameter only if you want to change the logical drive owner.
readCacheEnabled The setting to turn on or turn off the read cache. To turn on the read cache, set this parameter to TRUE. To turn off the read cache, set this parameter to FALSE.
writeCacheEnabled The setting to turn on or turn off the write cache. To turn on the write cache, set this parameter to TRUE. To turn off the write cache, set this parameter to FALSE.
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.
addCapacity The setting to increase the storage size (capacity) of the logical drive for which you are defining properties. Size is defined in units of bytes, KB, MB, GB, or TB. The default value is bytes.
addDrives The setting to add new disk drives to the logical drive. Specify the enclosure ID value and the slot ID value for each disk drive that you assign to the logical drive. Enclosure ID values are 0 to 99. Slot ID values are 1 to 32. Enclose the enclosure ID values and the slot ID values in square brackets ([ ]). Use this parameter with the addCapacity parameter if you need to specify additional disk drives to accommodate the new size.
redundancyCheckEnabled The setting to turn on or turn off redundancy checking during a media scan. To turn on redundancy checking, set this parameter to TRUE. To turn off redundancy checking, set this parameter to FALSE.
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.
userLabel The new name that you want to give an existing logical drive. Enclose the new logical drive name in double quotation marks (“ ”).
preReadRedundancyCheck The setting to check the consistency of RAID redundancy data on the stripes during read operations. Do not use this operation for non-redundant logical drives, for example RAID Level 0. To check redundancy consistency, set this parameter to TRUE. For no stripe checking, set this parameter to FALSE.
accessLogicalDrive The logical unit number for the access logical drive. The logical unit number is the only property that you can set for the access logical drive.
logicalUnitNumber Specific mappings to an individual host. This parameter also assigns the host to a host group.
host The name of the host to which the logical drive is mapped. Enclose the host name in double quotation marks (“ ”).
hostGroup The name of the host group to which the logical drive is mapped. Enclose the host group name in double quotation marks (“ ”). defaultGroup is the host group that contains the host to which the logical drive is mapped.
Notes

Host I/O errors might result in arrays with more than 32 logical drives. This operation might also result in internal controller reboots due to the expiration of the timeout period before the operation completes. If you experience this issue, quiesce host I/O, and try the operation again.

When you use this command, you can specify one or more of the optional parameters.

You can apply these parameters to only one logical drive at a time:

Add Capacity, Add Disk Drives, and Segment Size

Setting the addCapacity parameter, the addDrives parameter, or the segmentSize parameter starts a long-running operation that you cannot stop. These long-running operations are performed in the background and do not prevent you from running other commands. To show the progress of long-running operations, use the show logicalDrive actionProgress command.

Access LogicalDrive

The access logical drive is the logical drive in a SAN environment that is used for in-band communication between the storage management software and the storage subsystem controller. This logical drive uses a LUN address and consumes 20 MB of storage space that is not available for application data storage. An access logical drive is required only for in-band managed storage subsystems. If you specify the accessLogicalDrive parameter, the only property you can set is the logicalUnitNumber parameter.

Cache Flush Modifier

Valid values for the cache flush modifier are listed in this table.

Value Description

Immediate

Data is flushed as soon as it is placed into the cache.

250

Data is flushed after 250 ms.

500

Data is flushed after 500 ms.

750

Data is flushed after 750 ms.

1

Data is flushed after 1 s.

1500

Data is flushed after 1500 ms.

2

Data is flushed after 2 s.

5

Data is flushed after 5 s.

10

Data is flushed after 10 s.

20

Data is flushed after 20 s.

60

Data is flushed after 60 s (1 min.).

120

Data is flushed after 120 s (2 min.).

300

Data is flushed after 300 s (5 min.).

1200

Data is flushed after 1200 s (20 min.).

3600

Data is flushed after 3600 s (1 hr).

Infinite

Data in cache is not subject to any age or time constraints. The data is flushed based on other criteria that are managed by the controller.
Cache Without Battery Enabled

Write caching without batteries enables write caching to continue if the controller batteries are completely discharged, not fully charged, or not present. If you set this parameter to TRUE without an uninterruptible power supply (UPS) or other backup power source, you can lose data if the power to the storage subsystem fails. This parameter has no effect if write caching is disabled.

Modification Priority

Modification priority defines the amount of system resources that are used when modifying logical drive properties. If you select the highest priority level, the logical drive modification uses the most system resources, which decreases the performance for host data transfers.

Cache Read Prefetch

The cacheReadPrefetch parameter enables the controller to 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.

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.

Minimum Firmware Level

5.00 adds the addCapacity parameter.

7.10 adds the preReadRedundancyCheck parameter.