The NS2000 snapshot backup tool ax_snapshot allows
you to quickly make a read-only copy of a virtual file system. IBM supports
use of ax_snapshot to make backups of all Rational® ClearCase® data,
including VOB data. The following command creates a snapshot on cache partition fsp1m0rd1s0 of
a virtual partition mounted at /vobstg:
ax_snapshot ckpt /vobstg fsp1m0rd1s0
As
with any VOB backup strategy, you must lock the VOB before backing it up.
Because the snapshot backup copy can be made quickly, lock time required for
the backup is minimal.
By default, NS2000 file-based backup does not
back up files larger than 2 GB. VOBs using schema version 54 may include some
files larger than 2 GB. To ensure that these files are included in hard-media
(file-based) backups of a snapshot cache, edit the file
/usr/AXndmp/etc/config on
the NS2000 as follows:
Note: When this option is enabled and a large file
is encountered during file-based backup, a proprietary extension to standard
GNU tar format is used instead of the standard GNU tar format. With this option
on, you may not be able to use the standard GNU tar command to recover data
from file-based backups.
A cached snapshot backup should also be backed up to hard media
such as tape or CD, using backup software (for example, the NS2000 utility
ax_gtar)
that will preserve all file system information, including ACLs if the file
system is used to hold VOBs or views served by a VOB or view server on Windows.
Note: To back up a cached snapshot, you must first mount it.