On Friday July 8, daniel@xxxxxxxxxxxx wrote: > On 8 Jul 2005, Molle Bestefich wrote: > >> On 8 Jul 2005, Melinda Taylor wrote: > >>> We have a computer based at the South Pole which has a degraded raid 5 > >>> array across 4 disks. One of the 4 HDD's mechanically failed but we have > >>> bought the majority of the system back online except for the raid5 > >>> array. I am pretty sure that data on the remaining 3 partitions that > >>> made up the raid5 array is intact - just confused. The reason I know > >>> this is that just before we took the system down, the raid5 array > >>> (mounted as /home) was still readable and writable even though > >>> /proc/mdstat said: > > > > On 7/8/05, Daniel Pittman wrote: > >> What you want to do is start the array as degraded, using *only* the > >> devices that were part of the disk set. Substitute 'missing' for the > >> last device if needed but, IIRC, you should be able to say just: > >> > >> ] mdadm --assemble --force /dev/md2 /dev/hd[abd]5 > >> > >> Don't forget to fsck the filesystem thoroughly at this point. :) > > > > At this point, before adding the new disk, I'd suggest making *very* > > sure that the event counters match on the three existing disks. > > Because if they don't, MD will add the new disk with an event counter > > matching the freshest disk in the array. That will cause it to start > > synchronizing onto one of the good disks instead of onto the newly > > added disk.... Happened to me once, gah. > > Ack! I didn't know that. If the event counters don't match up, what > can you do to correct the problem? The "--assemble --force" should result in all the event counters of the named drives being the same. Then it should be perfectly safe the add the new drive. I cannot quite imagine a situation as described by Molle. If it was at all reproducible I'd love to hear more details. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
