Dell DCL and 3 Betriebsanweisung PDF herunterladen (Seite 25)

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.

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 36 37

Keine Kommentare

Dell DCL and 3 Betriebsanweisung Seite 25