From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mike Snitzer" Subject: Re: Need clarification on raid1 resync behavior with bitmap support Date: Mon, 6 Aug 2007 11:30:28 -0400 Message-ID: <170fa0d20708060830r1b897539sad7b2cc8ef44f912@mail.gmail.com> References: <170fa0d20707210959q11153d38u3281062c98d3adb7@mail.gmail.com> <18084.22271.122052.80056@notabene.brown> <170fa0d20707230547y3accc5c9v14805fdb3637e9c0@mail.gmail.com> <18098.52840.936611.7816@notabene.brown> <170fa0d20708030641l258ff0adrfdfa7726f746969e@mail.gmail.com> <18099.40761.348959.46664@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <18099.40761.348959.46664@notabene.brown> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 8/3/07, Neil Brown wrote: > On Friday August 3, snitzer@gmail.com wrote: > > > > I hand-patched your change into a 2.6.20.1 kernel (I'd imagine your > > patch is against current git). I didn't see any difference because > > unfortunately both of my full resync scenarios included stopping a > > degraded raid after either: 1) having failed but not been removed a > > member 2) having failed and removed a member. In both scenarios if I > > didn't stop the array and I just removed and re-added the faulty drive > > the array would _not_ do a full resync. > > > > My examples clearly conflict with your assertion that: "This only > > works if the array has not been shut down and restarted." > > I think my changelog entry for the patch was poorly written. > What I meant to say was: > *before this patch* a remove and re-add only does a partial resync > if the array has not been shutdown and restarted in the interim. > The implication being that *after the patch*, a shutdown and restart > will not interfere and a remove followed by a readd will always do a > partial resync, even if the array was shutdown and restarted while > degraded. Great, thanks for clarifying. > > To be explicit: isn't the bitmap still valid on the fresh members? If > > so, why is raid1 just disregarding the fresh bitmap? > > Yes. Exactly. It is my understanding and experience that the patch I > sent fixes a bug so that it doesn't disregard the fresh bitmap. It > should fix it for 2.6.20.1 as well. > > Are you saying that you tried the same scenario with the patch applied > and it still did a full resync? How do you measure whether it did a > full resync or a partial resync? I must not have loaded the patched raid1.ko because after retesting it is clear that your patch does in fact fix the issue. FYI, before, I could just tell a full resync was occurring by looking at /proc/mdstat and the time that elapsed. Thanks for your help, any idea when this fix will make it upstream? regards, Mike