From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx08.extmail.prod.ext.phx2.redhat.com [10.5.110.12]) by int-mx04.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o4LIp97k029322 for ; Fri, 21 May 2010 14:51:09 -0400 Received: from Ishtar.sc.tlinx.org (ishtar.tlinx.org [173.164.175.65]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o4LIov48012073 for ; Fri, 21 May 2010 14:50:57 -0400 Received: from [192.168.3.12] (Athenae [192.168.3.12]) by Ishtar.sc.tlinx.org (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o4LIosMc019142 for ; Fri, 21 May 2010 11:50:56 -0700 Message-ID: <4BF6D60E.4020306@tlinx.org> Date: Fri, 21 May 2010 11:50:54 -0700 From: "Linda A. Walsh" MIME-Version: 1.0 References: <4BF5A883.7060503@tlinx.org> <20100521051021.GA1412@maude.comedia.it> <4BF62CBF.3070702@tlinx.org> In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Volume alignment over RAID Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Lyn Rees wrote: > > 192.00K is listed as the start of each! GRR...why would that >> be a default...I suppose it works for someone, but it's NOT a power of 2! >> Hmph! > > 192 is a multiplier of 64... so it's aligned - assuming you used the > whole disk as a PV (you didn't partition the thing first). --- Isn't 64 the amount written / disk, so the strip size is 256K? Wouldn't that make each strip have 1 64K chunk written odd, and the next 3 written in the next 'row'.... I suppose maybe it doesn't matter...but when you break the pv up into vg's and lvs, somehow it seems odd to have them all skewed by 64K... But I haven't worked with RAIDS that much, so it's probably just a conceptual thing in my head. Anyway...I wanted to redo the array anyway. I didn't like the performance I was getting, so thought I'd try RAID 50. I was only getting 150-300 on writes/reads on the RAID60 which seemed a bit low. I get more than that on a a 4-data-disk RAID5 (200/400). It's a bit of pain to do all this reconfiguring now, but better now than when they are all full! It was a mistake to do RAID60, though I don't know if the performance on a 10data-disk RAID6 would be any better for writes...still has to do alot of XORing even with a hardware card. I had 2x6 and am going to try 4x3disks, so my hmmm....I guess now that I think about it my strip size was really 8, not 4, since I had 2 of them. But I'll still have a strip width of 8 with 4x3 RAID5's. I don't know if it will be much faster or not...but guess I'll see.