Script Commands
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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 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
.
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 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.
book.book Page 157 Wednesday, June 8, 2011 12:20 PM
Содержание PowerVault MD3600f Series
Страница 1: ...Dell PowerVault Modular Disk Storage Arrays CLI Guide ...
Страница 44: ...44 About the Script Commands ...
Страница 114: ...114 Using the Remote Replication Premium Feature ...
Страница 311: ...Script Commands 311 ...
Страница 312: ...312 Script Commands ...
Страница 318: ...318 Sample Script Files ...
Страница 328: ...Index 328 ...