Create Disk Group

Create Disk Group

This command creates either a free-capacity physical disk group or one virtual disk on a set of unassigned physical disks.

Syntax

create diskGroup [userLabel] physical disks=(trayID1,slotID1 ... trayIDn,slotIDn) raidLevel=(0 | 1 | 3 | 5 | 6) [capacity=volumeCapacity owner=(a | b) cacheReadPrefetch=(TRUE | FALSE) segmentSize=segmentSizeValue usageHint=(fileSystem | dataBase | multiMedia)] [enclosureLossProtect=(TRUE | FALSE)]
Parameters

Parameter

Description

userLabel

The name that you want to give the new physical disk group. Enclose the new name in double quotation marks (" ").

physical disks

The physical disks that you want to assign to the virtual disk that you want to create. Specify the enclosure ID and slot ID for each physical disk that you assign to the virtual disk. 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 parentheses.

raidLevel

The RAID level of the physical disk group that contains the virtual disk. Valid values are 0, 1, 3, 5, or 6.

capacity

The size of the virtual disk that you are adding to the storage system. Size is defined in units of bytes, KB, MB, GB, or TB. Syntax examples are capacity=500bytes capacity=2gb

owner

The owner parameter defines which RAID controller module owns the physical disk group. Valid RAID controller module identifiers are a or b, where a is the RAID controller module in slot A, and b is the RAID controller module in slot B. If you do not specify an owner, the RAID controller module 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 RAID controller module writes on a single physical disk in a virtual disk before writing data on the next physical disk. Valid values are 8, 16, 32, 64, 128, 256, or 512.

usageHint

The setting 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 virtual disk. Valid values are fileSystem, dataBase, or multiMedia.

enclosureLossProtect

The setting to enforce enclosure loss protection when you create the physical disk group. To enforce enclosure loss protection, set this parameter to TRUE. The default value is FALSE.

Notes

The physical disks parameter lets you choose the number of physical disks that you want to use in the physical disk group. If you choose this option, you do not need to specify the physical disks by enclosure ID and slot ID. The RAID controller modules choose the specific physical disks to use for the physical disk group.
If you do not specify a capacity by using the capacity parameter, all of the physical disk capacity that is available in the physical disk group is used. If you do not specify capacity units, bytes is used as the default value.

Cache Read Prefetch

The cacheReadPrefetch command lets the RAID controller module copy additional data blocks into cache while the RAID controller module reads and copies data blocks that are requested by the host from the physical disks 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 system that you use, determine the number of additional data blocks that the RAID controller module 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 RAID controller module 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.
Segment Size

The size of a segment determines how many data blocks that the RAID controller module writes on a single physical disk in a virtual disk before writing data on the next physical disk. 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 RAID controller module at run time. If the value that you entered is not valid, the RAID controller module returns a list of valid values. Using a single physical disk for a single request leaves other physical disks available to simultaneously service other requests.
If the virtual disk 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 physical disks in the physical disk group that are used for data transfers.) In this case, multiple physical disks are used for the same request, but each physical disk 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 physical disks that are required to satisfy a data transfer request.
Enclosure Loss Protection

For enclosure loss protection to work, each physical disk in a physical disk group must be in a separate enclosure. If you set the enclosureLossProtect parameter to TRUE and have selected more than one physical disk from any one enclosure, the storage system returns an error. If you set the enclosureLossProtect parameter to FALSE, the storage system performs operations, but the physical disk group that you create might not have enclosure loss protection. Enclosure loss protection is not valid when you create virtual disks on existing physical disk groups.

Minimum Firmware Level

7.10

Parameter	Description
`userLabel`	The name that you want to give the new physical disk group. Enclose the new name in double quotation marks (" ").
`physical disks`	The physical disks that you want to assign to the virtual disk that you want to create. Specify the enclosure ID and slot ID for each physical disk that you assign to the virtual disk. 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 parentheses.
`raidLevel`	The RAID level of the physical disk group that contains the virtual disk. Valid values are 0, 1, 3, 5, or 6.
`capacity`	The size of the virtual disk that you are adding to the storage system. Size is defined in units of bytes, KB, MB, GB, or TB. Syntax examples are `capacity=500bytes capacity=2gb`
`owner`	The `owner` parameter defines which RAID controller module owns the physical disk group. Valid RAID controller module identifiers are a or b, where a is the RAID controller module in slot A, and b is the RAID controller module in slot B. If you do not specify an owner, the RAID controller module 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 RAID controller module writes on a single physical disk in a virtual disk before writing data on the next physical disk. Valid values are 8, 16, 32, 64, 128, 256, or 512.
`usageHint`	The setting 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 virtual disk. Valid values are fileSystem, dataBase, or multiMedia.
`enclosureLossProtect`	The setting to enforce enclosure loss protection when you create the physical disk group. To enforce enclosure loss protection, set this parameter to TRUE. The default value is FALSE.