From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id oAQ8F8wr137811 for ; Fri, 26 Nov 2010 02:15:08 -0600 Received: from smtp3-g21.free.fr (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id CAA6F1C774FA for ; Fri, 26 Nov 2010 00:16:45 -0800 (PST) Received: from smtp3-g21.free.fr (smtp3-g21.free.fr [212.27.42.3]) by cuda.sgi.com with ESMTP id 1oWQEKT1jDetxByk for ; Fri, 26 Nov 2010 00:16:45 -0800 (PST) Date: Fri, 26 Nov 2010 09:16:22 +0100 From: Emmanuel Florac Subject: Re: Verify filesystem is aligned to stripes Message-ID: <20101126091622.264830fa@galadriel.home> In-Reply-To: <4CEEE9BC.2030401@hardwarefreak.com> References: <4CED5BFC.8000906@shiftmail.org> <20101125054607.GM13830@dastard> <4CEE0995.9030900@hardwarefreak.com> <20101125101537.GD12187@dastard> <4CEEE9BC.2030401@hardwarefreak.com> Mime-Version: 1.0 List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Stan Hoeppner Cc: xfs@oss.sgi.com Le Thu, 25 Nov 2010 16:57:00 -0600 vous =E9criviez: > Looking at the stripe size, which is equal to 64 sectors per array > member drive (448 sectors total), how exactly is a sub 4KB mail file > (8 sectors) going to be split up into equal chunks across a 224KB RAID > stripe? It won't, it will simply end on one drive (actually one mirror). However because the mirrors are striped together, all drives in the array will be sollicited in my experience, that's why you need at least as many writing threads as there are stripes to reach the top IOPS. In your case, writing 56 4K files simultaneously will effectively write on all drives at once, hopefully (depends upon the filesystem allocation policy though). > Does 220KB of the stripe merely get wasted? = It's not wasted, it just remains unallocated. What's wasted is potential IO performance. What appears from the benchmarks I ran along the year is that anyway you turn it, whatever caching, command tag queuing and reordering your're using, a single thread can't reach maximal IOPS throughput on an array, i. e. writing on all drives simultaneously; a single thread writing to the fastest RAID 10 with 4K or 8K IOs can't do much better than with a single drive, 200 to 300 IOPS for a 15k drive. -- = ------------------------------------------------------------------------ Emmanuel Florac | Direction technique | Intellique | | +33 1 78 94 84 02 ------------------------------------------------------------------------ _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs