From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: How to configure 36 disks ? Date: Mon, 23 Mar 2009 11:35:08 -0400 Message-ID: <49C7AC2C.9090307@tmr.com> References: <5d96567b0903230659t734677a3pb4fd77cccb54008b@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, Linux RAID Mailing List , linux-xfs@oss.sgi.com, linux-aio@kvack.org, "linux-ide@vger.kernel.org" To: Raz Return-path: In-Reply-To: <5d96567b0903230659t734677a3pb4fd77cccb54008b@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Raz wrote: > Hello > I need to configure 3xDAS'es, each with 12 disks. > All three DAS'es are connected to a single machine. > I have the following requirements (in this order of importance) > from the storage: > > 1. redundancy. > having two disks failing in one raid5 breaks the entire raid. when > you have 30TB storage > it is a disaster. > > 2. performance. > My code eliminates Linux raid5/6 write penalty. I managed to do by > manipulating xfs and patching linux raid5 a bit. > > 3. modularity ( a "grow" and it will be nice to have "shrink" ) > file system and volume must be able to grow. shrinking is possible > by unifying multiple file systems > under unionfs or aufs. > > 4. Utilize storage size. > > I assume each disk is 1TB. > > ___ snip ___ > Any other ideas ? Yes, you have the whole solution rotated 90 degrees. Consider your original solution #2 below... You have no redundancy if one whole DAS box fails, which is certainly a possible failure mode. If you put the RAID0 horizontally, two arrays size six in each DAS, then RAID6 vertically, if one DAS fails completely you still have a functioning system, and the failure results for individual drives remains about the same, while the rebuild time will be longer. Solution #2 raid0 DAS1: raid6: D,D,D,D,D,D | raid6: D,D,D,D,D,D | | DAS2: raid6: D,D,D,D,D,D | xfs. raid6: D,D,D,D,D,D | | DAS3: raid6: D,D,D,D,D,D | raid6: D,D,D,D,D,D | In addition, you can expand this configuration by adding more DAS units. This addresses several of your goals. In practice, just to get faster rebuild as the array gets larger, I suspect you would find it was worth making the horizontal arrays RAID5 instead of RAID0, just to minimize time to full performance. -- bill davidsen CTO TMR Associates, Inc "You are disgraced professional losers. And by the way, give us our money back." - Representative Earl Pomeroy, Democrat of North Dakota on the A.I.G. executives who were paid bonuses after a federal bailout.