Toshiba Magnia 560S - Manual (Page 132)

Configuring Arrays and Logical Drives 114
MegaRAID BIOS Configuration Utility
does random read requests more often, choose a small stripe size. The default is 64
KB.
16. Set the Write Policy in the Advanced Menu.
Write Policy sets the caching method 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. This
is the default setting.
- 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-through caching has a data security advantage over write-back caching.
Write-back caching has a performance advantage over write-through caching.
17. Set the Read Policy in the Advanced Menu.
Read-policy enables the SCSI read-ahead feature for the logical drive. You can set
this parameter to Normal, Read-ahead, or Adaptive.
- Normal specifies that the controller does not use read-ahead for the current
logical drive.
- Read-ahead specifies that the controller uses read-ahead for the current logical
drive.
- Adaptive specifies that the controller begins using read-ahead if the two most
recent disk accesses occurred in sequential sectors. If all read requests are
random, the algorithm reverts to Normal; however, all requests are still
evaluated for possible sequential operation. This is the default setting.
18. Set the Cache Policy on the Advanced Menu.
Cache Policy This parameter applies to reads on a specific logical drive. It does not
affect the Read ahead cache.
- Cached I/O specifies that all reads are buffered in cache memory. This is the
default setting.
- Direct I/O specifies that reads are not buffered in cache memory. Direct I/O
does not override the cache policy settings. Data is transferred to cache and the
host concurrently. If the same data block is read again, it comes from cache
memory.
19. Press <Esc> to exit the Advanced Menu.
20. After you define the current logical drive, choose Accept and press <Enter>.
If space remains in the arrays, the next logical drive to be configured appears.
21. Press any key to continue, then respond to the Save prompt.
22. Repeat steps 8 to 21 to configure another logical drive.
If all array space is used, a list of the existing logical drives appears.
23. Initialize the logical drives you have just configured. See Section "Initializing
Logical Drives."