From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Goryachev Subject: Re: Running check and e2fsck simultaneously Date: Mon, 11 Nov 2013 09:54:16 +1100 Message-ID: <52800E98.3080105@websitemanagers.com.au> References: <527FCBAF.4070208@hardwarefreak.com> <58CD4AD8-0A1E-42E8-984D-F4727EE2B8F0@gmail.com> <527FDBC1.4000009@hardwarefreak.com> <20131111073428.583b83b2@notabene.brown> <52800A73.9020401@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52800A73.9020401@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids On 11/11/13 09:36, Stan Hoeppner wrote: > On 11/10/2013 2:34 PM, NeilBrown wrote: >> The firmware can only relocate a sector if it reads it when it is marginal >> but not yet completely lost. If a sector is not read for a long time and >> during that time the media degraded beyond recovery the firmware cannot do >> anything. But RAID1 can - it can get it from the other device. > But is a scrub required for this? Isn't this exactly what occurs during > normal operation with md/RAID1? I.e. a read fails with disk error, so > we grab the sector from the mirror? So what advantage is there to > scrubbing md/RAID1? Wouldn't a check of the raid cause each member to be read in full, therefore helping the disk to notice that the sector is marginal, and/or the RAID layer to notice that the sector is no longer readable and therefore read from the other member, and re-write the sector. Consider a sector that is very rarely accessed... Or are you suggesting that a smart command issued to the underlying devices can solve both of those scenarios? Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au