Protecting Btrfs file systems

Btrfs file systems can be included as file specifications for backup and restore commands, archive and retrieve commands, and on backup image and restore image commands. You can also specify Btrfs subvolumes as file specification to the backup and restore, and archive and retrieve functions. You cannot use the backup-archive client image backup or image restore commands on a Btrfs subvolume.

Btrfs file systems are supported on SLES 11 SP2, or later, on IBM®System x, System p, and System z®.

If you want to create a static image backup of the entire Btrfs file system, you must unmount all the subvolumes so the backup-archive client can unmount or mount the Btrfs file system during the backup process. You can avoid the mounting and unmounting requirements if you perform a snapshot-based image backup of the Btrfs file system instead of a static image backup.

Image backup and image restore functionality is not available for Btrfs subvolumes. If you try to back up a subvolume by using the image backup, the following message is displayed:

ANS1162E Filesystem could not be mounted

You can mount a Btrfs subvolume by using either the subvolume name or the subvolume ID.

On Btrfs file systems, journal backup can be performed both at the file system and the subvolume level. If you perform journal-based backups on a Btrfs file system, the journal that is created is for the entire file system; there is not a separate journal for each subvolume.

Restriction: On Linux systems, some file systems such as ext2, ext3, ext4, btrfs, and xfs use a universally unique identifier (UUID) to identify themselves to the operating system. If you create an image backup of such a volume and you restore it to a different location, you might have two volumes with the same UUID. If you use UUID to define your file systems in /etc/fstab, be aware that the backup-archive client might be unable to correctly mount the restored file system because the UUIDs conflict. To avoid this situation, restore the image to its original location. If you must restore it to a different location, change the UUID of either the original or restored volume before you mount the restored file system. Refer to the Linux documentation for instructions on how to change a UUID. You might also need to manually edit the /etc/fstab file so the original volume, the restored volume, or both volumes can be mounted.