User`s guide

StorageWorks RAID Array 200 Controller Installation and Standalone Configuration Utility
7–32 EK–SWRA2–IG. C01
7.3.2.2 Choosing a Caching Policy
The caching policy determines what procedure the RAID controller uses to write
data to the logical drives. You can choose one of the following caching policies:
• Write-Back caching: A caching policy in which the controller acknowledges
that a write operation has completed successfully before data is written to
the disks. If you choose this caching policy, you may increase the I/O
performance of your RAID subsystem.
We recommend that you select this caching policy only if your cache has
battery backup and you have enabled the battery backup. Without a battery
backup, if there is a power failure, you lose data in cache that is not yet
written to the disks.
• Write-Through caching: A caching policy in which the data is written to
disk before the controller acknowledges that a write operation is completed
successfully. If you choose this caching policy and there is a power failure,
you minimize the chance of data loss. This is the StorageWorks RAID Array
200 subsystem default caching policy.
NOTE
We strongly recommend a Write-Through caching
policy to eliminate the chance of data loss due to
a power failure.
To change the caching policy, follow these steps:
1. Use the up and down arrow keys to highlight the Toggle Write Policy option
on the Logical Drive Definition menu and press the Enter key. The cursor
moves to the Write Mode column of the logical RAID drives list and
highlights the write mode of the first logical RAID drive.
2. Press the Enter key to toggle the caching policy to Write-Back.
3. Use the arrow keys to move to another logical RAID drive and repeat Steps
1 and 2 for each logical RAID.
4. When you finish selecting cache policy for your logical RAID drives, press
the ESC key. The Logical Drive Definition menu appears.
5. Press the ESC key again. The View/Update Configuration menu appears.