Lenovo ThinkServer RD650, User Manual

Page: 140 / 418

LSI Corporation
- 140 -
12Gb/s MegaRAID SAS Software User Guide

March 2014
Chapter 5: The HII Configuration Utility
Managing Physical Drives
Table 30 Virtual Drive Policies
5.6 Managing Physical Drives
When you select Drive Management on the Main Menu , the Drive Management Selection dialog appears.
The menu lists all the physical drives that are connected to the controller. Highlight the drive you want to manage and
press Enter. The following dialog appears.
Property Description
Access The access policy for the virtual drive. The options are Read/Write , Read Only , and Blocked .
Current Write Cache
Policy Displays the current write cache policy. 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 .
Default Write Cache
Policy Displays the default write cache policy of the virtual drive.
Disable Background
Initialization (BGI) 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.
Read Cache Policy 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.
Drive Cache The disk cache policy for the virtual drive. The possible values are Unchanged , Enable , and Disable .
Input/Output (I/O) 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 the 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.