Re: raid5 two disk failure

On Tuesday November 1, usenet@saeder-krupp.com wrote:

Hi,

The story:

- raid5 set with four disks
- after power outage two disks were marked faulty
- reassembled the set with 3 disks (1,2,3)
- added the forth disk
- reconstruction of the set failed because of an uncorrectable sector of disk 3
- tried to reassemble the set with disk 1,2,4. Not possible because disk 4 is in
spare mode.

Any opportunities to get the set back with disks 1,2,4? Thanks in advance for 
your help.

mdadm v1.9.0
linux 2.6.12.3

Best bet is to re-create the array as in

 mdadm -C /dev/mdX -l5 -n4 1 2 missing 4

However make sure that if you used non-defaults for chunksize or
layout, you preserved those non-defaults.
e.g. run
  mdadm -E 1

first, and look at what it says for "Chunk Size" and "Layout", and
uses those explicitly.

(ofcourse, substitute the real device names for 1, 2, 4 above).

NeilBrown