Administrator Guide

If DNS server functionality is operational and reachable by the controller's nslookup service, the FQDN for each controller is also shown. If
nslookup output is not available, the domain name will show '-'.
NOTE: DNS settings are limited to SMTP server configuration for email notification only.
About replicating virtual volumes
Replication for virtual storage provides a remote copy of a volume, volume group, or snapshot on a remote system by periodically updating
the remote copy to contain a point-in-time consistent image of a source volume.
For information about replication for virtual storage, see Working in the Replications topic.
About the Full Disk Encryption feature
Full Disk Encryption (FDE) is a method by which you can secure the data residing on the disks. It uses self-encrypting drives (SED), which
are also referred to as FDE-capable disks. When secured and removed from a secured system, FDE-capable disks cannot be read by other
systems.
The ability to secure a disk and system relies on passphrases and lock keys. A passphrase is a user-created password that allows users to
manage lock keys. A lock key is generated by the system and manages the encryption and decryption of data on the disks. A lock key is
persisted on the storage system and is not available outside the storage system.
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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