From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asdo Subject: Re: Read errors on raid5 ignored, array still clean .. then disaster !! Date: Mon, 01 Feb 2010 13:45:53 +0100 Message-ID: <4B66CD01.7040202@shiftmail.org> References: <4B5F6C73.30707@texsoft.it> <20100127074138.GA9607@maude.comedia.it> <20100129214852.00e565c4@notabene> <4B647E0E.6050609@texsoft.it> <4B64A779.6070809@shiftmail.org> <4B65943A.4040800@shiftmail.org> <4B66B367.6030803@texsoft.it> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <4B66B367.6030803@texsoft.it> Sender: linux-raid-owner@vger.kernel.org To: Giovanni Tessore Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Giovanni Tessore wrote: > If you have a degraded array which gets an unrecoverable read error, > reconstruction is not feasible any more, the disk is mark failed and > the whole array fails. The you have to recreate with --force or > --assume-clean, start to backup data.. but on each other read errors > you get the array offline again ... recreate in --force mode .. and so > on (which needs skill and it's error prone). > Maybe would be useful to have unrecoverable read errors on degraded > array to: > 1) sent a big alert to admin, with detailed info > 2) don't fail the disk and whole array, but set it into readonly mode > 3) report read errors to the OS (as for a single drive) > > This would allow to do a partial backup and save as most data as > possible without having to tamper with create --force etc.. > Experienced use may still try to overcome the situation readding > devices (maybe one gone out simply due to timeout), with create > --force, etc.. but many persons may have big troubles doing so, and > they just see all their data gone, when just a few sectors over many > Tb are unreadable and most data cab be saved. I think if you set it to readonly mode, it wouldn't degrade further even on read error. I think I saw this from the source code, but now I'm not really sure any more. Do you want to check? If what I say is correct, you can get data out relatively easily with 1 operation. The array won't go down.