Dell 3 manual Set the Read Policy, 177

–In Write-backcaching, the controller sends a data transfer completion signal to the host when the controller cache has received all the data in a transaction. This setting is not recommended.

–In Write-throughcaching, 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 for cluster mode.

Write-throughcaching has a data security advantage over write-backcaching, whereas write-backcaching has a performance advantage over write-throughcaching.

18Set the Read Policy.

Read-aheadenables the SCSI read-ahead feature for the logical drive. You can set this parameter to No-Read-Ahead,Read-ahead, or Adaptive. Adaptive is the default setting.

–No-Read-Aheadspecifies that the controller does not use read- ahead for the current logical drive.

–Read-aheadspecifies 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 No-Read- Ahead, however, all requests are still evaluated for possible sequential operation.

19Set the Read Policy.

Cache Policy applies to reads on a specific logical drive. It does not affect the Read-aheadcache.

–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.

20Press <Esc> to exit the Advanced Menu.

21After you define the current logical drive, choose Accept and press <Enter>.

PERC 3 BIOS Configuration Utility

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