Re: Recover a XFS on raid -1 (linear) when one disk is broken

[Jan Banan <b@xxxxxxxxxxxx>]

> > I have a raid -1 (linear) on my RedHat Linux 9 system with XFS
> > 1.2.0.  The raid consists of 4 disks where the last disk now seem to
> > be broken.
> >    
>
> backups?
>  
I have some quite old backups. I'd like to try retrieve more recent data 
if possible.

> > Is it possible to in some way mount this raid system so that I can
> > recover the files stored on the first 3 disks of this raid -1
> > (linear)?
> >    
>
> you could replace the last disk with a sparse file and run xfs_repair,
> my gut feeling is that it won't work very well though since files will
> be spread over disks (maybe not badly, depends on access patterns) and
> also metadata on broken disks will refer to non-broken blocks and
> vice-versa
I suppose the best stradegy is to get a new disk of the same size and 
then try to copy the whole damaged disk with "dd" to the new disk and 
then try to startup the raid again and after that run xfs_repair. What 
arguments to "dd" would fit best in this case? I think I've read that 
"dd" will normally abort when it can't read from a damaged disk and the 
disk is quite big, 250 GB (Maxtor).

Since it is a 4 disk linear raid I hope most of the files are not spread 
over blocks on different disks since I suppose XFS (1.2.0) tries to 
store the files on blocks close to each other(?).

Anyone knows what normally has happened to a disk when  you suddenly can 
not read from some parts of the disk? I get these kind of errors:

   Jul 15 21:18:58 d kernel: hdh: dma_intr: status=0x51 { DriveReady 
SeekComplete Error }
   Jul 15 21:18:58 d kernel: hdh: dma_intr: error=0x40 { 
UncorrectableError }, LBAsect=243818407, high=14, low=8937383, 
sector=243818336
   Jul 15 21:18:58 d kernel: end_request: I/O error, dev 22:41 (hdh), 
sector 243818336

Can I do something to make it better? The disk is only one year old but 
maybe the temperature has been a little bit to high in the computer box.

Best regards and thanks for any kind of hint!
Jan