User`s guide

WebBIOS Configuration Utility 21
A larger stripe size produces higher read performance, especially if your
computer does mostly sequential reads. However, if your computer
does random read requests more often, choose a smaller stripe size.
Select the stripe size based on your performance testing.
4 Select the Read Policy.
The Read Policy controls the SCSI read-ahead feature for the logical
drive. During a read operation, the read-ahead policy determines
whether the controller reads additional data records into cache. The
read-ahead feature allows your system to predict the next data that will
be read. If an application program reads data sequentially (as the disk
stores data), then read-ahead will improve performance, as this
reduces the time needed to access the data. Select the read policy
based on your performance testing. The options are as follows:
– Normal: The controller does not read additional records into
cache.
– Read-ahead: The controller reads additional records into cache.
– Adaptive (default): The controller begins using read-ahead if the
two most recent disk accesses occurred in sequential sectors. If all
read requests are random, the read policy reverts to Normal;
however, all requests are still evaluated for possible sequential
operation. Adaptive read-ahead is a good choice because it speeds
sequential read operations.
5 Select the Write Policy.
The Write Policy specifies whether I/O completion is signaled when
data is transferred to the cache or when it is written to disk. The
options are as follows:
– Write-back: The controller sends a data transfer completion signal
to the host when the controller cache has received all the data in a
transaction.
– Write-through (default): The controller sends a data transfer
completion signal to the host when all data in a transaction is
written to disk.
Write-through caching provides better data security than write-back
caching, and write-back caching offers higher throughput than write-
through caching. Write-back is safe to use only if the RAID controller
has battery-backed cache. Select the write policy based on your
performance testing.