Re: Disk I/O error while rebuilding an md raid-5 array

On Mon, 8 Feb 2010, Dawning Sky wrote:

Thanks for the good advice.  ddrescue on sdb returned an error of 4kB.
I do still have my old sde.  But one thing I did, which was stupid,
was trying to rebuild the raid-5 when it was mounted.  So I don't know
the old sde is still consistent with the rest 3 disks, since some
files would have been modified between the times when I took the old
sde offline and when the rebuild failed.

Please see the threads I have initiated the past 2-3 weeks, I had the 
exact same problem.

What you should do is just put in your new cloned drive, make sure it runs 
fine with 3 drives, and then start the rebuild with the drive that you 
were resyncing to. I've done this numerous times, and my experience says 
you will only have lost those 4 kilobytes of data that ddrescue couldn't 
read.

I'm now happily at RAID6 after doing a re-shape from 6 drive raid5-> 8 
drive raid6, change of SATA cables and a new marvell 8channel 
controller... No more read timeouts anyway, and I should be better 
protected from single read errors like you are having.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se