On Tue, 2013-12-10 at 08:59 +0000, Robin Hill wrote: > On Mon Dec 09, 2013 at 02:09:11PM +0000, Wilson Jonathan wrote: > > > After recovering from a failed raid6, now running with 2 missing drives > > and soon to be finally backed up (is still backing up), I have 2 related > > questions... > > > > The first is, can I add in both drives at the same time, or do I need to > > add them in singly, just checking for clarity? > > > You can add both together. Older versions of mdadm would kick off the > rebuild before the addition of both disks had been completed though, so > you might want to freeze the array first: > > echo freeze > /sys/block/md0/md/sync_action > mdadm /dev/md0 --add /dev/foo /dev/bar > echo idle > /sys/block/md0/md/sync_action > > > The second question is far more important... during the re-creation of > > data on the newly added missing disk/partition(s) does mdadm just read > > the data from the original array and write to the new disk(s) or does it > > potentially write new/update existing data (excluding bitmap/superblock) > > to the existing disks. > > > The rebuild process will only write data to the new disks. The only > cases where data will be written to the old disks during a rebuild is if > a read error is triggered and the data has to be reconstructed (not > applicable in your case as you have no redundancy to rebuild the data > from in the case of a read error), or if new data is written to the > array. > > Cheers, > Robin Wow that was a bum tightening 7 hours (I set the recovery to be slow[er], so I didn't tax the existing 4 drives, probably would have made no difference had I maxed it out but I do occasionally get a sata reset if doing things like DD and other things on disks that are under heavy load) The echo > freeze didn't work and came up with an error, so I tried > idle which it accepted... then did some googling and found that doing an idle to an array with multiple drive adds should stop and re-start it so even if the mdadm only tried to add 1 drive, it would then re-start and then add the 2 drives (was in a post on here by Niel Brown in 2012.) Thank you for your help, and Bernd Schubert who posted to my initial thread when I had problems, it was much appreciated. Jon. -- 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
