Dell PowerVault MD3000 - Manual (Page 156)

156
Script Commands
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.
CacheReadPrefetch
Cache read prefetch 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 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 configuration settings for the storage array 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.
Re-create Snapshot
This command starts a new copy-on-write operation by using an existing
snapshot virtual disk. You can re-create a single snapshot virtual disk or re-
create multiple virtual disks.
NOTE:
Refer to "Preparing Host Servers to Re-create a Snapshot Virtual Disk" on
page 75.
NOTICE:
Before you create a new point-in-time image of a source virtual disk, stop
any data access (I/O) activity or suspend data transfer to the source virtual disk to
ensure that you capture an accurate point-in-time image of the source virtual disk.
Close all applications, including Windows
®
Internet Explorer
®
, to make sure all I/O
activity has stopped.
NOTE:
Removing the drive letter of the associated virtual disk in Windows or
unmounting the virtual drive in Linux will help to guarantee a stable copy of the
drive for the Snapshot.
Syntax
recreate snapshot (virtualDisk [ virtualDiskName ] |
virtualDisks [ virtualDiskName1 ...
virtualDiskNamen ]) [userLabel=
" snapshotVirtualDiskName "