Accusys ExaRAID GUI - Manual (Page 206)

Advanced Functions
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If both controllers are down, the following pop-up dialog box will be
displayed to notify the user.
5.4 Snapshot
5.4.1 Introduction
Snapshot allows you to create instantaneous data images of a volume at
designated points in time. Unlike traditional data copy, which takes hours
or even days for data replication, depending on the size of the volume,
the snapshot function can create a copy of a volume of any size within
seconds. In addition, creating a snapshot volume requires only partial
capacity of the original volume, so snapshot is indeed a convenient
solution in terms of time and capacity efficiency.
Because the snapshot is done at the array and block level by leveraging
the computing power of the RAID controller, it is host-independent, and
application-independent. It also causes less performance impact
comparing to host-based snapshot software solutions.You are also
allowed to restore data of a LUN using snapshot restore function. As the
data image can be rolled back to a snapshot immediately, you may
resume your applications without waiting time.
Below are a few examples of using the snapshot function:
• Disk-based Full-image Backup and Restore
With snapshots of a volume at different points in time, you can retrieve
files of old revisions or restore deleted files simply by mounting the LUN of
the snapshot volumes. Contrary to tape-based backup, backup and
data restoration is simpler and faster.
Figure 5-14 Controller failback message
Figure 5-15 Error message indicates both controller failures