From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Wieser Subject: Re: Migrating a RAID 5 from 4x2TB to 3x6TB ? Date: Tue, 9 Jun 2015 20:46:12 +0200 (CEST) Message-ID: <1222347192.1017.1433875572719.JavaMail.zimbra@wieser.fr> References: <167089395.613.1433791723592.JavaMail.zimbra@wieser.fr> <55767860.5000803@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55767860.5000803@gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Can Jeuleers Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids ---- Original Message ----- > On 08/06/15 21:28, Pierre Wieser wrote: > > Hi all, > > > > I currently have an almost full RAID 5 built with 4 x 2 TB disks. > > I wonder if it would be possible to migrate it to a bigger RAID 5 > > with 3 x 6TB new disks. > > I'd recommend against it: > > https://en.wikipedia.org/wiki/RAID#Unrecoverable_read_errors_during_rebuild Oop's! I was not conscious at all of this issue. It happens that I am currenly living dangerously as I have another RAID 5 11,5 TB device :( I had already seen various administration issues when the size increases to this level, but I tought this was only an issue regarding the volumes organization (not tought deeply enough, obviously).... Starting from your link, and searching a bit, I understand now that the 10TB is a maximal limit for desktop-grade disks (regarding the URE at least). And thus for any element of a RAID device which needs to be scanned at recovery time. Apart from my poor english, would you say I'm right with this ? Does linux-raid have any recommandation(s) when managing more than 10TB of data ? I may imagine: - several smaller RAID 5 devices - would RAID10 be a valuable solution in your opinion ? (as a precision, all my servers have been migrated to CentOS 7.1) Nonetheless, I thank you very much for the link, which may prevent me to lose a big bunch of data ! > Jan > Pierre