Dell PERC 4/DC User Manual download pdf (Page 30)

The drive displays as HOTSP.

5. Save the configuration.



Objects Menu

1. On the Management Menu select Objects—> Physical Drive.



A physical drive selection screen appears.

2. Select a hard drive in the READY state and press <Enter> to display the action menu for the drive.

3. Press the arrow keys to select Make HotSpare and press <Enter>.



The selected drive displays as HOTSP.



Creating Arrays and Logical Drives



Configure arrays and logical drives using Easy Configuration, New Configuration, or View/Add Configuration. See Using Easy Configuration, Using New

Configuration, or Using View/Add Configuration for the configuration procedures.



After you create an array or arrays, you can select the parameters for the logical drive. Table5-1 contains descriptions of the parameters.



Table 5-1.LogicalDriveParametersandDescriptions

Parameter

Description

RAID Level

The number of physical drives in a specific array determines the RAID levels that can be implemented with the array.

Stripe Size

Stripe Size specifies the size of the segments written to each drive in a RAID 1, 5, or 10 logical drive. You can set the stripe size to 8 KB, 16

KB, 32 KB, 64 KB, or 128 KB. The default is 64 KB.

A larger stripe size provides better 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.

Write

Policy

Write Policy specifies the cache write policy. You can set the write policy 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. This setting is recommended in standard mode.



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.

Write-through caching has a data security advantage over write-back caching. Write-back caching has a performance advantage over write-

through caching.



NOTICE: If WriteBack is enabled and the system is quickly turned off and on, the RAID controller may hang when flushing cache memory.

Controllers that contain a battery backup will default to WriteBack caching.

NOTE: You should not use write-back for any logical drive that is to be used as a Novell NetWare volume.

NOTE: Enabling clustering turns off write cache. PERC 4/DC and PERC 4e/DC support clustering.

Read

Policy

Read-ahead enables the read-ahead feature for the logical drive. You can set this parameter to Read-Ahead, No-Read-ahead, or Adaptive.

The default is Adaptive.

Read-ahead specifies that the controller uses read-ahead for the current logical drive. Read-ahead capability allows the adapter to read

sequentially ahead of requested data and store the additional data in cache memory, anticipating that the data will be needed soon. Read-

ahead supplies sequential data faster, but is not as effective when accessing random data.

No-Read-Ahead specifies that the controller does not use 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.

Cache

Policy

Cache Policy applies to reads on a specific logical drive. It does not affect the Read-ahead cache. The default is Direct I/O.

Cached I/O specifies that all reads are buffered in cache memory.

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