Re: raid5 recover after a 2 disk failure

[David Greaves <david@dgreaves.com>]

All looked OK, a few comments...

Frank Jenkins wrote:
Logically this comes first...
> This should force the array back into a useable state,
> yes? 
> (assuming that I'm correct and sde isn't really
> busted).
correct.
Since you have a spare you may want to use ddrescue to transfer data from sde to 
the spare as a 'backup'. That way, if you do get problems with sde you have the 
best chance of recovery.

If you do that, then you can use the backup as your new sde.

either way...

> I think what I need to do is run:
> mdadm -ARf /dev/md1 missing /dev/sd[baed]1
I don't think you want -R.
If enough drives are present to provide data then it will run with a -f.

If you get the order wrong here, it won't damage anything *provided you have a 
missing disk and the array is degraded* (which you do) so there is no need to 
worry about having rw devices.

The event counts from abcdf are the same and sde is only slightly off so you 
should find it assembles just fine.

At this point can copy data off the disks - bear in mind you may have fs or data 
corruption due to the inconsistency in sde.

If you are confident that sde is actually OK, you can now add in the spare:
   mdadm /dev/md1 --add /dev/sdc1
and allow a rebuild.

Then do an xfs_repair (or ext3 or whatever).
You can do this whilst the resync is running.

At that point you should be back up and running - no need for a restore.


> And more importantly, if anyone can tell me how to
> lock down the 
> disks so they are readonly so I can play around with
> mdadm 
> re-assembly options without having to worry about
> compeletly 
> destroying the array, that'd be awesome.
Not sure you can do this.

> As usual, any help would be greatly appreciated.
> 
> I'll include the -E output from the drives in their
> current state, if that helps:
It did.