Create RAID Virtual Disk (Free Capacity Base Select)

Create RAID Virtual Disk (Free Capacity Base Select)

This command creates a virtual disk in the free space of a disk group.

Syntax

create virtualDisk diskGroup=volumeGroupNumber userLabel="virtualDiskName" [freeCapacityArea=freeCapacityValue capacity=volumeCapacity owner=(a | b) cacheReadPrefetch=(TRUE | FALSE) segmentSize=segmentSizeValue usageHint=(fileSystem | dataBase | multiMedia)]

Parameters

Parameter Description

diskGroup
The sequence number of the disk group in which you want to create the new virtual disk. (To determine the sequence numbers of the disk groups in your storage array, enter the show storageArray Profile command.)

userLabel
The name you want to give the new virtual disk. Enclose the new virtual disk name in double quotes (" ").

freeCapacityArea
The index number of the free space in an existing disk group that you want to use to create the new virtual disk. Free capacity is defined as the free capacity between existing virtual disks in a disk group. For example, a disk group might have the following areas: virtual disk 1, free capacity, virtual disk 2, free capacity, virtual disk 3 free capacity. To use the free capacity following virtual disk 2, you would specify:

freeCapacityArea=2.

Use the show diskGroup command to determine if free capacity area exists.

capacity
The size of the virtual disk you are adding to the storage array. Size is defined in units of bytes, KB, MB, or GB.

owner
The RAID controller module that owns the virtual disk. 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
This parameter turns on or turns 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 kilobytes) 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 This parameter sets both the cacheReadPrefetch and segmentSize parameters to default values. The default values are based on the typical I/O usage pattern of the application using the virtual disk. Valid values are fileSystem, dataBase, or multiMedia.

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 RAID controller module owns the virtual disk. The preferred RAID controller module ownership of a virtual disk is the RAID controller module that currently owns the disk group.

If you do not specify a capacity, all available capacity in the free capacity area of the disk group is used. If you do not specify capacity units, bytes are used as the default.

The size of a segment determines how many data blocks 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 blocks 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 provided by the RAID controller module at run time. If the value you enter is not valid, the RAID controller module returns a list of valid values. For optimal performance in a multi-user database or file system storage environment, set your segment size to minimize the number of physical disks needed to satisfy a data transfer request. 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 a single-user large data transfer environment (such as multi-media) performance is maximized when a single data transfer request is serviced with a single data stripe. (A data stripe is the segment size multiplied by the number of physical disks in the disk group that are used for data transfers.) In this case, multiple disks are used for the same request, but each disk is only accessed once.

If you set the cache block size to 16, then you cannot create a virtual disk with a segment size of 8.

Cache read prefetch enables the RAID controller module to copy additional data blocks into cache while the RAID controller module reads and copies data blocks requested by the host from disk 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 number of additional data blocks that the RAID controller module reads into cache is determined by the storage array configuration settings that you use. Valid values for the cacheReadPrefetch parameter are 0 or 1. If you enter any value greater than 1, the RAID controller module treats that value as if it were a 1 and turns on cache read prefetch.

You do not have to enter a value for the cacheReadPrefetch parameter or the segmentSize parameter. If you do not enter a value, the firmware uses the usageHint parameter with the fileSystem argument as the default value. If you choose to enter a value for the cacheReadPrefetch parameter or a value for the segmentSize parameter, you cannot use the usageHint parameter.

Minimum Firmware Level

5.20

Parameter	Description
`diskGroup`	The sequence number of the disk group in which you want to create the new virtual disk. (To determine the sequence numbers of the disk groups in your storage array, enter the show storageArray Profile command.)
`userLabel`	The name you want to give the new virtual disk. Enclose the new virtual disk name in double quotes (" ").
`freeCapacityArea`	The index number of the free space in an existing disk group that you want to use to create the new virtual disk. Free capacity is defined as the free capacity between existing virtual disks in a disk group. For example, a disk group might have the following areas: virtual disk 1, free capacity, virtual disk 2, free capacity, virtual disk 3 free capacity. To use the free capacity following virtual disk 2, you would specify: freeCapacityArea=2. Use the `show diskGroup` command to determine if free capacity area exists.
`capacity`	The size of the virtual disk you are adding to the storage array. Size is defined in units of bytes, KB, MB, or GB.
`owner`	The RAID controller module that owns the virtual disk. 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`	This parameter turns on or turns 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 kilobytes) 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`	This parameter sets both the cacheReadPrefetch and segmentSize parameters to default values. The default values are based on the typical I/O usage pattern of the application using the virtual disk. Valid values are fileSystem, dataBase, or multiMedia.