Dell PowerEdge RAID Controller 6i - Manual (Page 84)

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Configuring and Managing RAID
Table 6-2. Virtual Disk Parameters and Descriptions
Parameter Description
RAID Level RAID Level specifies the whether the virtual disk is RAID 0, 1,
5, 6, 10, 50, and 60. The RAID level you select depends on the
number of disks, disk capacity, and the requirements for fault
tolerance and performance. See "Summary of RAID Levels" on
page 17 for more information.
Stripe Element Size Stripe Element Size specifies the size of the segments written
to each physical disk in a RAID 0, 1, 5, 6, 10, and 50 virtual
disk. You can set the stripe element size to 8 KB, 16 KB, 32 KB,
64 KB, 128 KB, 256 KB, 512 KB, or 1024 KB. The default and
recommended stripe element size is 64 KB.
A larger stripe element size provides better read performance if
your system does mostly sequential reads.
Write Policy Write Policy specifies the controller write policy. You can set
the write policy to Write-Back or Write-Through.
In Write-Back caching, the controller sends a data transfer
completion signal to the host when the controller cache has
received all the data in a transaction.
NOTE:
If a BBU is present, the default cache setting is
Write-Back cache. If no BBU is present, the default cache policy
default setting is Write-Through.
NOTICE:
If Write-Back is enabled and the system is quickly
turned off and then on, the controller may pause as the system
flushes cache memory. Controllers that contain a battery backup
default to Write-Back caching.
In Write-Through caching, the controller sends a data transfer
completion signal to the host when the disk subsystem has
received all the data in a transaction.
Write-Back caching has a performance advantage over Write-
Through caching.
NOTE:
Certain data patterns and configurations perform better
with Write-Through cache policy.
Dell_PERC6.1_UG.book Page 84 Wednesday, April 15, 2009 4:18 PM