From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piotr Legiecki Subject: Re: RAID10 failed with two disks Date: Tue, 23 Aug 2011 10:35:20 +0200 Message-ID: <4E536648.3060803@pum.edu.pl> References: <4E5231EE.3010001@pum.edu.pl> <20110822210903.2582bcfd@notabene.brown> <4E5240BE.1050807@pum.edu.pl> <20110822220129.5b2928ff@notabene.brown> <4E525122.7090607@pum.edu.pl> <20110823095634.398f2118@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110823095634.398f2118@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids >> Hura, hura, hura! ;-) Well, wonder why it didn't work for me ;-( > > Looks good so far, but is you data safe? I think so. fsck has found some errors and corrected them. resync done cat /sys/block/md4/md/mismatch_cnt 0 Looks good. > This is correct assuming the default layout. > If you asked for "--layout=n3" you would get a 3-way mirror over a1,b1,c1 and > d1,e1,f1 and those would be raid0-ed. And the question which one is the most efficient is beyond the scope of our subject I'm of course? Or maybe there is some general rule of thumb for this? The more disks the faster array should be *but* the more data to mirror at once when writing... Anyway my tests proved that RAID1 on two disks is *much* slower than RAID10 on 4 disks. RAID10 SATA can easily compete with HP SmartAray P410i/BBC SAS RAIDs (but in RAID1 only ;-)). Well, at least during iozone benchmarks. > If you had 5 devices then you get data copied on > sda1+sdb1 > sdc1+sdd1 > sde1+sda1 > sdb1+sdc1 > sdde+sde1 > > so is *any* pair of adjacent devices fail, you lose data. So from safety point of view there is need for more spare disks or go for RAID6. > Hard to tell without seeing kernel logs. Almost certainly a hardware issue > of some sort. Maybe a loose or bumped cable. Maybe a power supply spike. > Maybe a stray cosmic ray.... http://pastebin.com/iapZWm0S Those 'failed' disks are connected to motherboard SATA ports. I've got also Adaptec 1430 adapter with 2 free ports, maybe I should move those disks there. Thank you for all the help and time put into answering my questions. Piotr