From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756805AbZKUTVy (ORCPT ); Sat, 21 Nov 2009 14:21:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755479AbZKUTVx (ORCPT ); Sat, 21 Nov 2009 14:21:53 -0500 Received: from mail-vw0-f192.google.com ([209.85.212.192]:41075 "EHLO mail-vw0-f192.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754546AbZKUTVx (ORCPT ); Sat, 21 Nov 2009 14:21:53 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=JeRxMUkre60A5wlTQJ9lERybEIuDOmpCI7U6uWRCbpJpkOn4Guv3tEYpR+I6aByJ5s FyJyWRYd5vzdQrkVfJr2Jhko8cZtkEQKlyif4TOrp4+ArW/KBAx3mSbKgk/X348KAc03 FOTTfpr9ol5d9rs49OVm/GO7/L5MYNoxxs/b0= MIME-Version: 1.0 In-Reply-To: <20091121170355.7540d169@mjolnir.ossman.eu> References: <20091008163952.679572b5@mjolnir.ossman.eu> <20091121170355.7540d169@mjolnir.ossman.eu> Date: Sat, 21 Nov 2009 12:21:58 -0700 X-Google-Sender-Auth: e6b509825e193566 Message-ID: Subject: Re: Raid not shutting down when disks are lost? From: Dan Williams To: Pierre Ossman Cc: neilb@suse.de, LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 21, 2009 at 9:03 AM, Pierre Ossman wrote: > Neil? > > On Thu, 8 Oct 2009 16:39:52 +0200 > Pierre Ossman wrote: > >> Today one RAID6 array I manage decided to lose four out of eight disks. >> Oddly enough, the array did not shut down but instead I got >> intermittent read and writer errors from the filesystem. This is expected. The array can't shutdown when there is a mounted filesystem. Reads may still be serviced from the survivors, all writes should be aborted with an error. >> >> It's been some time since I had a failure of this magnitude, but I seem >> to recall that once the array lost too many disks, it would shut down >> and refuse to write a single byte. The nice effect of this was that if >> it was a temporary error, you could just reboot and the array would >> start nicely (albeit in degraded mode). >> >> Has something changed? Is this perhaps an effect of using RAID6 (I used >> to run RAID5 arrays)? Or was I simply lucky the previous instances I've >> had? It should not come back up nicely in this scenario. You need "--force" to attempt to reassemble a failed array. >> >> Related, it would be nice if you could control how it handles lost >> disks. E.g. I'd like it to go read-only when it goes in to fully >> degraded mode. In case the last disk lost was only a temporary glitch, >> the array could be made to recover without a lengthy resync. >> When you say "fully-degraded" do you mean "failed"? In general the bitmap mechanism provides fast resync after temporary disk outages. -- Dan