From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: 5 drives lost in an inactive 15 drive raid 6 system due to cable problem - how to recover? Date: Thu, 9 Sep 2010 07:35:30 +1000 Message-ID: <20100909073530.1e5da34d@notabene> References: <4C87C656.2030405@stern.nyu.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C87C656.2030405@stern.nyu.edu> Sender: linux-raid-owner@vger.kernel.org To: Norman White Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Wed, 08 Sep 2010 13:22:30 -0400 Norman White wrote: > 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. What sort of different advice? From whom? This should either do exactly what you want, or nothing at all. I suspect the former. To be more confident I would need to see the output of mdadm -E /dev/sd[b-p] NeilBrown > > 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html