Lenovo ThinkServer RD650 User Manual page 103

12Gb/s MegaRAID SAS Software User Guide
March 2014
Table 23 Virtual Drive Policies
Property
Strip Size
Read Policy
Write Policy
I/O Policy
Access Policy
Drive Cache
Disable Background
Initialization (BGI)
Default Initialization
The following table describes the RAID levels that you can select when creating a new virtual drive. Some system
configurations do not support RAID 6 and RAID 60.
The virtual drive strip size per DDF. The possible values are as follows:
 0: 512 bytes
1: 1 KB

 2: 2 KB
 3: 4 KB
 4: 8 KB
 ...
8: 1 MB

The read cache policy for the virtual drive. The possible values are as follows:
 Ahead: The controller reads sequentially ahead of requested data and stores the additional data in
cache memory, anticipating that the data will be needed soon. This process speeds up reads for
sequential data, but provides little improvement when accessing random data.
 Normal: Read-ahead capability is disabled.
The write cache policy for the virtual drive. The possible values are as follows:
 Write-through (WThru): The controller sends a data transfer completion signal to the host when
the virtual drive has received all of the data and has completed the write transaction to the drive.
 Write-back (WBack): The controller sends a data transfer completion signal to the host when the
controller cache has received all of the data in a drive write transaction. Data is written to the virtual
drive in accordance with policies set up by the controller. These policies include the amount of dirty
and clean cache lines, the number of cache lines available, and the elapsed time from the last
cache flush.
 Force Write Back.
The I/O policy for the virtual drive. The possible values are as follows:
Direct: Data reads are not buffered in cache memory. Data is transferred to cache and the host

concurrently. If the same data block is read again, it comes from cache memory. (The I/O policy
applies to reads on a specific virtual drive. It does not affect the read ahead cache.)
Cached: All reads are buffered in cache.

The access policy for the virtual drive. The options are Read/Write, Read Only, and Blocked.
The disk cache policy for the virtual drive. The possible values are Unchanged, Enable, and Disable.
Specifies whether background initialization is enabled or disabled. When BGI is enabled, the firmware
runs the initialization process in the background. When BGI is disabled, the initialization process does not
start automatically and does not run in the background.
Allows choice of virtual drive initialization option. The possible options are No, Fast, and Slow.
LSI Corporation
Description
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Chapter 5: The HII Configuration Utility
Managing Configurations