PERC - настройка оптимизации raid-массивов

PERC - Dell PowerEdge RAID Controller.

Read policy

  • Read-Ahead. When using read-ahead policy, the controller reads sequential sectors of the logical drive when seeking data. Read-ahead policy may improve system performance if the data is actually written to sequential sectors of the logical drive.
  • No-Read-Ahead. Selecting no-read-ahead policy indicates that the controller should not use read-ahead policy.
  • Adaptive Read-Ahead. When using adaptive read-ahead policy, the controller initiates read-ahead only if the two most recent read requests accessed sequential sectors of the disk. If subsequent read requests access random sectors of the disk, the controller reverts to no-read-ahead policy. The controller continues to evaluate whether read requests are accessing sequential sectors of the disk, and can initiate read-ahead if necessary.

Write Policy

Note: Storage Management does not allow you to select the Write-Back policy for controllers that do not have a battery. This restriction protects a controller without a battery from the data loss that may occur in the event of a power failure. On some controllers, the Write-Back policy may be available in the controller BIOS even though it is not available in Storage Management.

  • Write-Back. When using write-back caching, the controller sends a write-request completion signal as soon as the data is in the controller cache but has not yet been written to disk. Write-back caching may provide improved performance since subsequent read requests can more quickly retrieve data from the controller cache than they could from the disk. Write-back caching also entails a data security risk, however, since a system failure could prevent the data from being written to disk even though the controller has sent a write-request completion signal. In this case, data may be lost. Other applications may also experience problems when taking actions that assume the data is available on the disk.
  • Write-Through. When using write-through caching, the controller sends a write-request completion signal only after the data is written to the disk. Write-through caching provides better data security than write-back caching, since the system assumes the data is available only after it has been safely written to the disk.

Stripe Element Size

8 kb - 1 Mb

Для хранения корреспонденции выставил = 64kb ( тесты показали самую высокую производительность дисковых операций с множеством файлов)

Note. Blocksize для файловой системы равен 4 kb

Disk Cache Policy

Next, I think that disk cache policy refers to whether you want to use the controller cache to cache IOs. (Далее, я думаю, что disk cache policy относится к тому, хотите ли вы использоваль кэш контроллера для cache IOs, или нет.)

Моя конфигурация

Read policy: Adaptive Read-Ahead
Write Policy: Write-Back
Stripe Element Size: 64KB
Disk Cache Policy: Enabled

Ссылки

 
blog/2011/12/13-perc_-_соображения_по_оптимизации_raid-массивов.txt · Последние изменения: 2011/12/13 17:08 — Антон Бугреев · []