[dm-devel] dm-cache refusing to come up again after a crash

[Joe Thornber]

On Fri, Dec 06, 2013 at 08:16:05PM +0100, Steinar H. Gunderson wrote:
> On Fri, Dec 06, 2013 at 05:57:13PM +0000, Joe Thornber wrote:
> > Yep, grab:
> > 
> > https://github.com/jthornber/thin-provisioning-tools
> > 
> > build, and then try cache_check on it (which should tell you what's
> > wrong).  Other programs to play with are cache_dump, cache_restore and
> > cache_repair.
> 
> Well, first of all, it doesn't compile, since you use typename outside of
> templates :-) Fixing that is easy, though. But afterwards:

Grr, I thought that was fixed, what version of g++ are you using?

> 
> root at ubuntu:~/thin-provisioning-tools# ./cache_check /dev/md1
> examining superblock
>   superblock is corrupt
>     bad checksum in superblock
> 
> So where do I want to go from there? cache_dump doesn't want to play with the
> superblock because the checksum is bad... do I want cache_repair, then? Do I
> want to take a backup of anything first?

Ouch.  Could you go through what happened please?  Did dm-cache crash,
or did the machine die for some other reason?

- Joe