On Wed, Sep 10, 2014 at 9:05 PM, Gregory Farnum <greg at inktank.com> wrote: >> Related, given there is no fsck, how would one go about backing up the >> metadata in order to facilitate DR? Is there even a way for that to >> make sense given the decoupling of data & metadata pools...? > > Uh, depends on the kind of DR you're going for, I guess. There are > lots of things that will backup a generic filesystem; you could do > something smarter with a bit of custom scripting using Ceph's rstats. I do think this is something we could think about building a tool for: lots of people will have comparatively tiny quantities of metadata so full dumps would be a nice thing to have in our back pockets. Reminds me of the way Lustre people used LVM snapshots for their metadata. Some users have set maintenance windows in which even a purely offline metadata dump tool could be useful. The other one would be the tool for rebuilding an approximate metadata picture from the backtraces of objects in the data pool. It's a degenerate case of an online backward scrub where you create a fresh filesystem and add the old/orphaned data pool to it, but it's such a simple thing that it's tempting to implement it as a separate tool as well/in advance. John
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