From mboxrd@z Thu Jan 1 00:00:00 1970 From: Norman White Subject: 5 drives lost in an inactive 15 drive raid 6 system due to cable problem - how to recover? Date: Wed, 08 Sep 2010 13:22:30 -0400 Message-ID: <4C87C656.2030405@stern.nyu.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids We have a 15 drive addonics array with 3 5 port sata multiplexors, one of the sas cables was knocked out to one of the port multiplexors and now mdadm sees 9 drives , a spare, and 5 failed, removed drives (after fixing the cabling problem). A mdadm -E on each of the drives, see 5 drives (the ones that were uncabled) as seeing the original configuration with 14 drives and a spare, while the other 10 drives report 9 drives, a spare and 5 failed , removed drives. We are very confident that there was no io going on at the time, but are not sure how to proceed. One obvious thing to do is to just do a: mdadm --assemble --force --assume-clean /dev/md0 sd[b,c, ... , p] but we are getting different advice about what force will do in this situation. The last thing we want to do is wipe the array. Another option would be to fiddle with the super blocks with mddump, so that they all see the same 15 drives in the same configuration, and then assemble it. Yet another suggestion was to recreate the array configuration and hope that the data wouldn't be touched. And even another suggestion is to create the array with one drive missing (so it is degraded and won't rebuild) Any pointers on how to proceed would be helpful. Restoring 30TB takes along time. Best, Norman White