Re: Error mounting multi-device fs after restart

[cwillu <cwillu@cwillu.com>]

On Tue, Feb 8, 2011 at 3:59 PM, Diwaker Gupta <diwaker@maginatics.com> wrote:
>> Define *indefinitely*.
>
> Meaning the messages continued for as long as the system was under observation.
>
>> Are the drives not working?
>
> I believe they are. Working in the sense that I can read off data
> using 'dd', I can inspect partition tables etc.
>
>> If the drives are working, have you tried waiting 2-3 days, possibly longer?
>> 10TB is a *lot* of data
>
> The system was running overnight when I first hit the problem. On
> subsequent reboots, I've only waited less than half an hour. Usually
> the mount is instantaneous, so I wasn't sure if waiting would help at
> all. The error messages did not indicate that the system could recover
> at that stage. If there's even a slight chance that the fs would
> eventually mount, I'm happy to let it run for a day or two. Note that
> if I mount using the 'degraded' option, the mount succeeds but
> subsequent attempts to read the data fail.

Huh.  How do those attempts fail?

Try mounting ro, or degraded,ro, and reading the data off.  That
worked for me recently on a broken btrfs raid10 (and didn't on another
one, so your mileage may vary).

There's also the perpetually imminent fsck development which might save the day.