Dell PowerEdge H730P User Manual page 43

4. Initialize the virtual disks.
NOTE: When you use one physical disk group to create multiple virtual disks, all the virtual disks
must be configured with the same RAID level.
When you define the virtual disks, you can set the following virtual disk parameters:
• RAID level
• Stripe element size
• Read policy
• Write policy
• Type of initialization
• Hot spare configuration
NOTE: The default hard drive cache policy for a virtual disk with SAS hard drives is disabled
and virtual disk with SATA hard drives is enabled. The Virtual Disk parameter cannot be
changed in the BIOS Configuration Utility (<Ctrl> <R>). Use Dell OpenManage Storage
Management for the hard drive cache setting operation.
The following table shows the parameters that you can configure when defining virtual disks.
Table 4. Parameters — Description
Parameter
RAID Level
Stripe Element Size Specifies the size of the segments written to each physical disk in a RAID 0, 1,
Write Policy
Description
Specifies whether the virtual disk is RAID 0, 1, 5, 6, 10, 50, or 60. The number
of disks, disk capacity, requirements for fault tolerance, performance, and
capacity should be considered when selecting the RAID level. For more
information, see Summary Of RAID
5, 6, 10, 50, and 60 virtual disk. You can set the stripe element size to 64 KB
128 KB, 256 KB, 512 KB, or 1 MB. The default and recommended stripe
element size is 64 KB.
A larger stripe element size provides better read performance if your system
mostly does sequential reads.
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 Battery Backup Unit (BBU) is present, the default cache setting
is Write-Back. If no BBU is present, the default cache policy default
setting is Write-Through.
NOTE: If Write-Back is enabled and the system is turned off and then on,
the controller may pause as the system flushes cache memory.
Controllers have 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.
Levels.
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