On Tue, 12 Oct 2010 16:27:53 +0200 Simon S <simon@xxxxxxxxx> wrote: > Hi all, > > I had a config with 5 disks and 3 raid 5 arrays: > > md2 : system root > md3 : swap > md4 : data > > I added a 6th disk with the intention of growing my raid5 into raid6. > > The step I used were : > > # mdadm /dev/mdX -a /dev/newdiskX > # mdadm -G --level 6 -n 6 /dev/mdX --backup-file /mdXbackup > (yes, with backup file on root partition md2...) Bad idea.. Very bad idea. > > The md3 array reshaped without any problem. > md2 seemed to reshape well until it reaches 50.4%, then the rebuild speed stalled at 14Kb/s. This is the expected consequence of that bad idea. Unfortunately it would be hard to reliably get mdadm to complain about that, though I guess the common cases are easy to protect against ... added to 'todo' list > md4 was still in the state "resync=DELAYED" then. > > As the rebuild process seemed hung, I restart the machine ... bad idea. Not really, nothing else would have worked. > > Now mdadm refuses to assemble md2 and md4, and displays this message : > > mdadm: Failed to restore critical section for reshape, sorry. > Possibly you needed to specify the --backup-file > > md2 is my linux installation, not very bad if I lose this one. > > md4 however contains valuable data. > > While md4 was still in the state resync=DELAYED before the shutdown, I expect > it should not has been (to much) modified and can be recovered. Very true. > > Any idea on how I could safely do it ? > > Should I give a try to the hack "Get 'Grow_restart' to always return 0." > mentionned by Neil Brown on 22 april 2010 in this mailing list ? That is your best bet. I plan to make that easier to do in mdadm-3.2 (no recompile necessary). Before you do, check "mdadm -E /dev/newdiskX" and make sure the "Reshape position" is 0. If it is you should be fine. I It won't be for md2 of course. So md will quite possible have some corruption. Run fsck on it an it will probably be mostly OK, but there is a reasonable chance that some files will be corrupted. Whether and when you will notice is impossible to guess. NeilBrown > > > Thank for any advices, > > Cheers, > -- 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
