Disk and File System Management3-23
Example: A messaging application or a database application stores user data in one
or two files that can grow to several hundred GB in a volume. If, for some reason, this
application corrupts the files, you can revert the volume to a snapshot taken before
the data corruption.
Example: You can revert a volume used as a test environment to its original state
after each test.
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This section describes two considerations you must make before deciding whether
you should use SnapRestore to revert a volume.
Time require d for data recove ry: If the amount of corrupted data is small, it is easier
to copy the files from a snapshot or restore the files from tape than to use SnapRe-
store for these reasons:
You can preserve the data in other files in the same volume.
The filer does not need to reboot.
If the amount of data to be recovered is large, it takes a long time to copy the files
from a snapshot or to restore from tape. In this case, SnapRestore is the preferred
method for recovering from data corruption.
Free space required for data recovery: If a file to be recovered needs more space
than the amount of free space in the active file system, you cannot copy the file from
the snapshot to the active file system. For example, if a 10-GB file is corrupted and
only 5 GB of free space exists in the active file system, you cannot copy the file from
a snapshot to recover the file. In this case, SnapRestore can quickly recover the file;
you do not have to spend time making the additional space available in the active file
system.
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The following list describes how SnapRestore and SnapMirror interact with each
other:
You can revert a volume that is the source volume for data replication. You can-
not, however, revert a volume that is currently the mirror for data replication.
You can revert to any snapshot that is displayed by the snap list command.
That is, you can revert to a regular snapshot or a snapshot created by SnapMirror
for data replication. The snapshots created by SnapMirror have a different naming
convention than the regular snapshots, as explained in the section, Snapshots
Created During Data Replication, in Chapter 16.
If you have both regular and SnapMirror snapshots in the volume, avoid reverting
to a snapshot taken before the SnapMirror snapshot. If you must revert to a snap-
shot taken before the SnapMirror snapshot, after the reversion, the volume
contains no SnapMirror snapshot that is essential for the incremental update of
the mirror. The filer must re-create the base-line version of the mirror.