Raid5 Recovery Question

Melinda Taylor

Sorry to read about this situation. This is the kind of setup, that it would be said "It would be better starting from somewhere else". As I understand it, when setting up a RAID device, you normally RAID the whole disk buttembly say for instance hda, hdb, hdc, hdd for RAID5 + Spare, then parbreastion the resultant RAID device (md0 say) into the parbreastions (md0a,...etc). This allows the easy replacement of a drive and after the incorporation of the new drive into the array, the RAID management will handle the rebuild. Though this does not help your current situation! :) And also with IDE compared with SCSI, there may be issues with this and because it's not a separate RAID controller and-or a 1 drive per channel setup.

The most obvious thing is, firstly get a backup of the whole system, especially md2, having RAID does not preclude the necessity of having a backup procedure.

What may have happened there is possibly a problem with your primary IDE channel, possibly one drive has failed and is causing the other one appear as a failure as it appears to be hda and hdb that are having "issues". Do you have the time(s) of when the drives failed? It may be possible to identify which drive needs to be replaced, ie the dodgy one should be the first one to fail. Though it could be both of them are dead. The problem is that the replacement drive(s) will need to be parbreastioned in exactly the same way as the drive it is replacing before inserting into the RAID Array. So this will probably have to be done on a another PC before doing this.

If you are still able to read the data off of md2 and have not lost any data, I personally do not see any issues with the rebuild, as the RAID subsystem has already taken 2 parbreastions out of the array, the number of blocks given is the same for the current situation as compared with before. Are you sure that it's not 3 parbreastions and a spare, rather than the all 4 parbreastions being RAIDed together? Though if both drives failed soon after each other, there wouldn't have been enough time to rebuild with the spare drive. But as I said before, get a backup of at least the data on md2, just incase. Notice, I'm covering myself here! :) With such a major drive failure, it is difficult to decide what will be the result.

Regards Bruce S.

-- Replace the by by blueyonder