Administrator Guide

A system and the FDE-capable disks in the system are initially unsecured but can be secured at any point. Until the system is
secured, FDE-capable disks function exactly like disks that do not support FDE.
Enabling FDE protection involves setting a passphrase and securing the system. Data that was present on the system before
it was secured is accessible in the same way it was when it was unsecured. However, if a disk is transferred to an unsecured
system or a system with a different passphrase, the data is not accessible.
Secured disks and systems can be repurposed. Repurposing a disk changes the encryption key on the disk, effectively erasing all
data on the disk and unsecuring the system and disks. Repurpose a disk only if you no longer need the data on the disk.
FDE operates on a per-system basis, not a per-disk group basis. To use FDE, all disks in the system must be FDE-capable. For
information on setting up FDE and modifying FDE options, see Changing FDE settings.
NOTE: If you insert an FDE disk into a secured system and the disk does not come up in the expected state, perform a
manual rescan. See Rescanning disk channels.
About data protection with a single controller
The system can operate with a single controller if its partner has gone offline or has been removed. Because single-controller
operation is not a redundant configuration, this section presents some considerations concerning data protection.
The default caching mode for a volume is write back, as opposed to write through. In write-back mode, the host is notified
that the controller has received the write when the data is present in the controller cache. In write-through mode, the host is
notified that the controller has received the write when the data is written to disk. Therefore, in write-back mode, data is held in
the controller cache until it is written to disk.
If the controller fails while in write-back mode, unwritten cache data likely exists. The same is true if the controller enclosure
or the enclosure of the target volume is powered off without a proper shutdown. Data remains in the controller cache and
associated volumes will be missing that data on the disk.
If the controller can be brought back online long enough to perform a proper shutdown and the disk group is online, the
controller should be able to write its cache to disk without causing data loss.
If the controller cannot be brought back online long enough to write its cache data to disk, please contact technical support.
To help prevent data loss in case the controller fails, you can change the caching mode of a volume to write through. While
this will cause significant performance degradation, this configuration guards against data loss. While write-back mode is much
faster, this mode is not guaranteed against data loss in the case of a controller failure. If data protection is more important, use
write-through caching. If performance is more important, use write-back caching.
For more information about volume cache options, see About volume cache options. For more information about changing cache
settings for a volume, see Modifying a volume. For more information about changing system cache settings, see Changing
system cache settings.
Getting started
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