User's Manual

Controllers 135
Data in the cache may also be lost in case of unintended cable or power
failure. In the event of such a failure, Storage Management preserves the data
written on the preserved or dirty cache until you recover the virtual disk or
clear the cache.
This feature is available only on SAS controllers with firmware version 6.1 and
later.
The status of the controller is affected by the preserved cache. The controller
status is displayed as degraded if the controller has preserved cache.
CAUTION: You may not be able to use Storage Management to manage the
preserved cache in some cases. As an example, consider you have a RAID 1 level
with two disks—D1 and D2. If you now remove D2, the virtual disk is degraded and
the data in the controller cache is written to D1. At this point, D1 has the latest
data. Now, if you re-insert D2 and pull out D1, the virtual disk is still degraded and
does not have the latest data.
Manage Preserved Cache
You can discard the preserved cache only if all of the following conditions are
met:
• The controller does not have any foreign configuration. Select Click for
Preview
to view details of the foreign configuration. See Foreign
Configuration Operations.
• The controller does not have any offline or missing virtual disks. If there
are offline or missing virtual disks, ensure you have a backup of these
virtual disks.
• Cables to any virtual disk are not disconnected.