From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gionatan Danti Subject: Re: On URE and RAID rebuild - again! Date: Wed, 30 Jul 2014 15:05:29 +0200 Message-ID: <53D8ED99.90606@assyoma.it> References: <53D8ACF0.1070202@assyoma.it> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: linux-raid@vger.kernel.org, g.danti@assyoma.it List-Id: linux-raid.ids On 30/07/2014 13:13, Mikael Abrahamsson wrote: > > There has been much discussion about the URE figures. Some people > interpret it one way, others another way. There is nobody here that > knows for sure. Ask your HDD vendor, if they answer, do share here! > - Ouch! - I was hoping that HDD vendors were somewhat more open about their URE calculations... It's time for some lab test, I think! > > When MD encounters an URE, it should calculate that block from parity > information and write it. I have personally had problems with this not > happening, seems it might be that if the URE doesn't happen repeatedly, > MD might not re-write. All parity raid levels should behave the same, so > this should work identically for RAID1, RAID10, RAID5 and RAID6. > What about _degraded_ array state? In other words, if a degraded RAID5 experiences a URE during rebuild, what happens? I read that most hardware based RAID card both stop rebuilding _and_ kill the entire array. From my understanding, mdadm should stop rebuilding but the array can the restarted, mounted and backupped. Right? Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8