Users Guide

Managing The Preserved Cache

The Managed Preserved Cache feature provides you the option to ignore or restore the controller cache data.

In the write-back policy, data is written to the cache before being written to the physical disk. If the virtual disk goes oine or is

deleted for any reason, the data in the cache is lost.

Data in the cache may also be lost in case of unintended cable or power failure. If 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 rmware version 6.1 and later.

The status of the controller is aected 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. So, 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.

You can discard the preserved cache only if all of the following conditions are met:

• The controller does not have any foreign conguration. Select Click for Preview to view details of the foreign conguration. See

Foreign Conguration Operations.

• The controller does not have any oine or missing virtual disks. If there are oine or missing virtual disks, ensure that you have a

backup of these virtual disks.

• Cables to any virtual disk are not disconnected.

Encryption Key

The controller uses the encryption key to lock or unlock access to SED. You can create only one encryption key for each encryption-

capable controller.

If you are using LKM, you must create the encryption key by providing the Encryption Key Identier and the Passphrase.

Encryption Key Identier

An Encryption Key Identier is a user-supplied text label for the Passphrase. The identier helps you determine which Passphrase

to provide while authenticating import of foreign encrypted SED drives.

Passphrase

A Passphrase is a user supplied string that the controller uses to create the encryption key.

NOTE: For more information on Encryption Key and Passphrase guidelines, click the icon on the Manage Encryption

Key

page.