[ILUG] RAID-5 recovery

[Niall O Broin]

On 27 Feb 2012, at 23:22, Ronan Cunniffe wrote:

>    (yeah, first post to the list in ages, and it's 'cos I need help.... )
> 
>    I have an mdadm RAID-5 array with - you guessed it - 2 failed disks.
> 
>    Well, somebody else had it and didn't monitor it; so now it's dead, and has landed on my desk (the data is irreplaceable, of course).
> 
>    Some dd_rescue'ing later, I have images of all the disks, 2 of them with ~5-10% unreadable each.  The good news is that the unreadable bits mostly don't overlap, so I actually have N-1 good data for ~99% (maybe all - still checking) of the array, and so it's at least theoretically possible to reconstruct the whole thing.
> 
> Clearly, I need a tool that lets me nominate which-disk-is-dead for different block ranges.  I don't think mdadm will help, so does anybody know of anything like this?

Never came across anything like that, but two thoughts occur:

1) Get another disk, and assemble it from the readable parts 2 slightly dead disks.

2) Write a kernel module which returns blocks from disk A when asked for blocks from disk B for the relevant block ranges.



Niall