From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: raid6 rebuild Date: Wed, 11 Apr 2007 11:43:20 +1000 Message-ID: <17948.15672.420527.629228@notabene.brown> References: <20070404194638.GB3712@xi.wantstofly.org> <20070405055030.GA6978@xi.wantstofly.org> <4614FF86.3020007@tmr.com> <20070405140626.GA8726@xi.wantstofly.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Dan Williams on Thursday April 5 Sender: linux-raid-owner@vger.kernel.org To: Dan Williams Cc: Lennert Buytenhek , Bill Davidsen , mingo@redhat.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thursday April 5, dan.j.williams@intel.com wrote: > On 4/5/07, Lennert Buytenhek wrote: > > On Thu, Apr 05, 2007 at 09:54:14AM -0400, Bill Davidsen wrote: > > > > > I confess, I would feel safer with my data if the rebuild started > > > over, I would like to be sure that when it (finally) finishes the > > > data are valid. > > > > With disk #3 about to die, I'd have felt safer if it first finished > > rebuilding the replacement disk for failed disk #1 (that rebuild had > > almost completed at that point), safeguarding the array against a > > third disk failure. > > > I agree, the current arrangement seems to throw away a significant > amount of work. Yes, you will need to resync when re-adding the > second disk, but in the meantime might as well try to get a redundant > mode at all costs. Yes, I think you are right. If you want it to restart from the beginning you can alway abort the current resync by 'echo idle > sync_action'. The question is: is it really as simple to do as it sounds. I seem to remember that aborting the recovery on any error was any easy way to avoid some nasty race, but I have no idea what the race was. One would need the enumerate all the interesting cases and make sure they will all work as expected. I cannot think of an problems immediately but that doesn't mean there aren't any... It is now on my todo list... NeilBrown