Re: xfs_metadump as a backup tool

[Gionatan Danti <g.danti@assyoma.it>]

Il 21-08-2017 22:11 Eric Sandeen ha scritto:
> Short answer is "No," because:
> xfs_metadump is only a diagnostic tool.  It is not tested or supported
> for any other use.
> 
> If nothing else, on a normal live filesystem your metadata and data is
> constantly changing; if you replay old metadata over a filesystem,
> you'll end up pointing to file data blocks that are incorrect.
> 
> If you really truly have only statically-allocated files from start to
> finish, then maybe...
> 
> But more than anything else, the tool was not designed or tested for
> anything other than developer diagnostics.
> 
> For disaster recovery, having periodic metadata snapshots might come
> in handy from a forensic POV, but I would not rely on this as a
> primary part of your normal backup/recovery scheme.

Hi Eric,
thank for your reply. From xfs_metadump man page is read that the tool 
should be only used as a debugging aid, but hey - maybe someone used it 
in more clever ways ;)

> If you've already done a proper backup wit tar/rsync/(xfsdump?) then
> you have everything you need to restore the filesystem without
> resorting to xfs_metadump cleverness, right?

Sure, but restoring metadata on a corrupted, but healty, volume would be 
much faster than restoring both data and metadata. As a first-stop 
recovery, maybe it was worth a try. But if nobody is doing that, it 
should not be a good idea...

> No, it's not possible to preallocate space on xfs without marking it
> as unwritten.

Understood.
Thanks Eric.

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Danti Gionatan
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