(original article)

Re: Converting RAID5 to RAID6 and other shape changing in md/raid

31 October 2010, 23:38 UTC

As a user with recent successes and failures (as seen in previous posts).

I "believe" I was able to convert a 1TBx6 into a 2TBx6or7 by repartitioning (delete/recreate) and growing the array. A few suggestions (0) Upgrade mdadm to the latest version (compile it) (1) backup (2) backup (3) SCRUB the new drive (badblocks -w, or dd /dev/zero), scrub again. (4) convert to RAID6 (add a new controller, hang drives outside the case, if you have to) (5) then add new drives.

I say "believe" because at least twice now I've gotten bit by by a failure midway through reshaping the raid (converting raid5-6 or adding a drive) and had trouble continuing the process after reboot. The first time I forced the array which probably worked, unfortunately, my new sata controller (added after the failure) was silently corrupting the array so I'm not sure...

Note to Neil: Just today I had a problem restarting an array 6x25G (thankfully) and the "solution" was to upgrade from "mdadm - v3.1.2 - 10th March 2010" to "mdadm - v3.1.4 - 31st August 2010" (via git). Prior to the upgrade, assemble using a backup file, gave a seg-fault (sorry, I seem to have lost the trace) after the upgrade the array assembled no problems. So the moral of the story is use the latest version of mdadm!