Veritas Netbackup: Part 3- UNIX Raw Partitions

Caution Save a copy of the partition table before performing raw-partition backups so you have it for reference prior to a restore. To restore the raw partition, a device file must exist and the partition must be the same size as when it was backed up. Otherwise, the results of the restore are unpredictable.

Notes On UNIX Raw-Partition Backups

• Use raw-partition backups only if you can ensure that the files are not changed in any way during the backup or, in the case of a database, if you can restore the database to a consistent state by using transaction log files.
• Do not perform archives of raw partitions on any client. An archive backs up the raw partition and then deletes the device file associated with the raw partition. However, the file system does not recover the space used by the raw partition.
• Before backing up file systems as raw partitions, unmount the file system to allow buffered changes to be written to the disk, and to prevent the possibility of the file system changing during the backup. You can use the bpstart_notify and the bpend_notify scripts to unmount and remount the backed-up file systems.
• The Cross Mount Points attribute has no effect on raw partitions. If the root partition is being backed up as a raw partition and has mount points for other file systems, the other file systems are not backed up, even if you select Cross Mount Points.
  

The same is true for the Follow NFS attribute. NFS file systems mounted in a raw partition are not backed up. Nor can you back up raw partitions from other machines by using NFS mounts to access the raw partitions. The devices are not accessible on other machines through NFS.

• For disks managed by disk volume managers such as VERITAS Volume Manager (VxVm), specify the logical partition names.
• For clients in a FlashBackup policy, refer to the NetBackup Advanced Client System Administrator’s Guide (backup selection list and cache section) for the differences between Standard and FlashBackup policies.

When to Use Raw-Partition Backups
If there are no file systems to back up and the disks are used in raw mode (such as with some databases), back up the disk partitions as raw partitions. When backing up databases as raw partitions, you can use the bpstart_notify and bpend_notify scripts to do the preprocessing and postprocessing necessary to back up the databases.

You can also perform a raw-partition backup of a disk partition used for file systems. A disadvantage of this method is that you must restore the entire partition to recover a single file (unless you are using FlashBackup). To avoid overwriting the entire partition, use the redirected restore feature to restore the raw partition to another raw partition of the same size, and then copy individual files to the original file system.

Raw-partition backups are also useful for backing up entire disks. Since the overhead of the file system is bypassed, a raw-partition backup is usually faster. The size of the raw-partition backup will be the size of the entire disk, regardless of whether the entire disk is used.

To specify a UNIX raw partition in the policy backup selection list, enter the full path name of the device file. For example, on Solaris:
/devices/sbus@1,f8000000/esp@0,800000/sd@2,0:1h

Caution Do not specify wildcards (such as /dev/rsd*) in paths for raw-partition backups. Doing so can prevent the successful restore of entire devices, if there is overlap between the memory partitions for different device files.

You can include raw partitions in the same backup selection list as other backups. For example:
/home
/usr
/etc
/devices/sbus@1,f8000000/esp@0,800000/sd@2,0:1h

Note NetBackup does not distinguish between full and incremental backups when backing up a raw partition. The entire partition is backed up in both cases.

Raw-partition backups occur only if the absolute file path in the backup selection list is a block or character special-device file. You can specify either block or character special-device files; although, character special-device files are often faster because character devices avoid the use of the buffer cache for accessed disk data. To obtain the optimum backup speed for raw-partition backups, test both a block and character special-device file to ensure the best choice for your platform.

Ensure that you are specifying the actual block-or character-device files. Sometimes, these are links to the actual device files. If a link is specified, only the link is backed up. If the device files are reached while backing up /dev, NetBackup backs up only the inode files for the device, not the device itself.

Selecting a Schedule Backup Type for a UNIX Raw Partition
When performing a raw partition backup, be sure to select Full Backup for the Type of Backup from the Schedules tab. Any other backup type will not work for backing up raw partitions. (See “Type of Backup” on page 146 of the Netbackup Guide.)