Using NS2000 Snapshot Backups

About this task

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 DevOps Code 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.

Procedure

  1. Locate the following line: #ALLOW_TAR_EXTENSION # auspex extension to support large files (>=2GB)
  2. Remove the first comment delimiter (#) to enable this feature. ALLOW_TAR_EXTENSION # auspex extension to support large files (>=2GB)

What to do next

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.