ZyXEL Communications NSA-2401 User Manual page 197

To use a snapshot to restore files, use the MyNSA screens, CIFS (Windows Explorer), or FTP
to browse to the snapshot image folder. The snapshot folder contains images named after the
folders and files in the volume at the time of the backup. To restore a folder or file to its state
at the time of the snapshot, open the snapshot image of the same name. You can also copy or
move the snapshot image to another folder (outside the snapshot folder).
When you use a snapshot to restore files, the NSA keeps intermediate snapshots between the
snapshot you use and the present. For example, say you had the NSA take daily snapshots and
on Friday you choose to use Monday's snapshot; the NSA keeps the Tuesday, Wednesday, and
Thursday snapshots .
Although you can continue to work while the NSA takes a snapshot, it's a good idea to
schedule snapshots for non-peak times so not very many files are open. Snapshots may get
progressively slower as more are done but they are still very fast compared to backups (as only
block changes are recorded).
The NSA automatically purges snapshots.
See Snapshot Purging on page 213
Snapshots Versus Backups
See Section 9.2 on page 198
1 A snapshot only records changes to files within a volume, so it's faster and takes up less
space than a backup.
2 You must create a snapshot of a complete volume, not on a single file or folder as you
can do with a backup.
It's a good idea to take both snapshots and backups for the following reasons:
1 Snapshots may become invalid, so it's good to also have backups available in case that
happens. Backups are more reliable than snapshots.
2 Backups are more reliable than snapshots. So have backups available in case snapshots
become invalid.
3 Backups may require several hours depending on the amount of data you have to back up
(it's a good idea to schedule backups at non-peak times), so you should take a snapshot
of your data before the backup is run. If a file becomes corrupt during the backup, you
can still revert to the previous snapshot and back up again.
4 If files to be backed up are open at the time of the backup, then make sure that snapshots
are allowed. If they are allowed and files are open at the time the backup is run, then
backup first takes a snapshot and then copies the files from this snapshot.
A backup proceeds without the snapshot if there is not enough space for the
snapshot, but if an open file changes during the backup, the backup fails.
NSA-2401 User's Guide
for details.
for more information on backups.
Chapter 9 Protect Screens
197