From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Tripathy Subject: Re: Raid Checks Date: Sun, 03 Apr 2011 20:02:49 +0100 Message-ID: <4D98C459.40806@abpni.co.uk> References: <4D983064.30808@abpni.co.uk> <4D98346F.8090502@abpni.co.uk> <20110403210157.2c3ac83d@notabene.brown> <4D98544E.9000107@abpni.co.uk> <20110403211937.0a6efdee@notabene.brown> <4D985A3B.8030801@abpni.co.uk> <4D9865AC.6060607@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D9865AC.6060607@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids > On 03/04/2011 12:30, Jonathan Tripathy wrote: >>>> This is what state my server is currently in: >>>> >>>> State : clean, resyncing >>> With mdadm 3.2.1, this will show "checking" when it is checking, >>> rather than "resyncing". >> Interesting. So during a normal "resync", I'm guessing redundancy will >> be lost? > > You only need a resync when you've already lost redundancy. The only > normal resync is at array creation time, when mdadm will instantly > create the array with no redundancy and then proceed to generate the > mirror/parity information. Any other resync is only required after > something else caused a loss of redundancy e.g. a disc dying or a > system crash, or perhaps a drive threw up a bad sector. The check > process will attempt to discover any such problems. Understood. If a problem is detected, would I have to involk a re-sync manually (assuming that CHECK is enabled in the script) > > As Doug Ledford noted in the Red Hat Bugzilla there are times when a > md RAID 1 can harmlessly end up out of sync. > >> Also, if the "checking" process finds an error, where will I >> find it? /var/log/messages? > > In the email the raid-check process sends you. Any errors found are > not reported in detail on RHEL/CentOS 5 - I think more recent > kernel/mdadm can be asked to be more verbose about the location of > errors. Requesting a repair rather than a check would get the check > process to automatically resync any stripes which had bad mirrors/parity. How do I set up emails? Is it just the monitor deamon? > > In short, it is safe to ignore a modest mismatch_cnt on RAID 1 as long > as you aren't seeing disc errors, and that is what Doug Ledford's > patch to raid-check does. >