xfs_metadump as a backup tool

Gionatan Danti
2017-08-21T19:59:04Z

Hi all,
I wish to ask if someone is using xfs_metadump as a "real" backup tool -
ie: in production.

I was wondering how to lower recovery time in case of filesystem
corruption, and the idea of using xfs_metadump + xfs_mdrestore struck
me.

I plan to have a single, relatively big XFS volume with an handfull of
fully preallocated large files (VM disk images). Basically, I was
thinking about:
- take a LVM snapshot;
- mount the snap volume as read-only;
- copy the user data (via tar/rsync/whatever);
- additionally, xfs_metadump its metadata content.

If a major filesystem corruption occour, as a first step I should be
able to simply restore its metadata with xfs_mdrestore and re-gain
access to files/data blocks. A potential pitfall would be related to
extents that at the time of xfs_metadump where marked as "unwritten" but
later were written - restoring the old metadata will immediately turn
user data into zeroes. It is possible to fully allocate a file *without*
marking the allocated extents as "unwritten"? Yes, I know this has
security implications...

Is this a good idea? I am missing something?
Thanks.