Dell PERC 4/DC - Manual (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 to display the action menu for the drive.
3. Press the arrow keys to select Make HotSpare and press .
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.