LSI SCSI 320-0 Configuration page 33

Using New Configuration,
Step
9 Open the Advanced menu to set the remaining options.
Stripe size This parameter specifies the size of the segments written to each disk in a
RAID 1, 3, 5, 10, 30 or 50 logical drive. You can set the stripe size to 2 KB, 4
KB, 8 KB, 16 KB, 32 KB, 64 KB, or 128 KB. A larger stripe size produces
higher read performance, especially if your computer does mostly sequential
reads. However, if you are sure that your computer does random read requests
more often, select a small stripe size. The default stripe size is 64 MB.
Write Policy This option 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.
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. This is the default
setting.
Write-through caching has a data security advantage over write-back caching, whereas
write-back caching has a performance advantage over write-through caching. You should
not use write-back for any logical drive that is to be used as a Novell NetWare volume.
Read-ahead This option 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.
This is the default setting.
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.
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.
Direct I/O specifies that reads are not buffered in cache memory. This is the default
setting.
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.
Press <Esc> to exit the Advanced Menu.
10 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. Repeat steps 6 to 9
to configure another logical drive. If the array space has been used, a list of the existing
logical drives appears. Press any key to continue and respond to the Save prompt.
11 Initialize the logical drives you have just configured. See Initializing Logical Drives on
page 29.
Continued
Action
Chapter 2 MegaRAID Configuration Utility
25