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 q13MAIQx163808 for ; Fri, 3 Feb 2012 16:10:19 -0600 Received: from smtp.pobox.com (b-pb-sasl-quonix.pobox.com [208.72.237.35]) by cuda.sgi.com with ESMTP id GiDSC34qSTjVyXq8 for ; Fri, 03 Feb 2012 14:10:17 -0800 (PST) Date: Fri, 3 Feb 2012 22:10:15 +0000 From: Brian Candler Subject: Re: Performance problem - reads slower than writes Message-ID: <20120203221015.GA2675@nsrc.org> References: <20120130220019.GA45782@nsrc.org> <20120131020508.GF9090@dastard> <20120131103126.GA46170@nsrc.org> <20120131145205.GA6607@infradead.org> <20120203115434.GA649@nsrc.org> <4F2C38BE.2010002@hardwarefreak.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4F2C38BE.2010002@hardwarefreak.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Stan Hoeppner Cc: Christoph Hellwig , xfs@oss.sgi.com On Fri, Feb 03, 2012 at 01:42:54PM -0600, Stan Hoeppner wrote: > You've hit the peak read rate of these Hitachi drives. As others > pointed out, if you need more read performance than the dozen of these > you plan to RAID stripe, then you'll need to swap them for units with a > faster spindle: > > 7.2k 1.21x > 10k 1.68x > 15k 2.53x > > or with SSDs, which will yield an order of magnitude increase. Your > stated need is 20M 500-800KB files, or 20GB if my math is correct. Thanks for your suggestion, but unfortunately your maths isn't correct: 20M x 0.65MB = 13TB. And that's just one of many possible datasets like this. I'm aware that I'm working with low-performance drives. This is intentional: we need low power consumption so we can get lots in a rack, and large capacity at low cost. Fortunately our workload will also parallelise easily, and throwing it across 24 spindles will be fine. But obviously I want to squeeze the most performance out of each spindle we have first. I'm very happy to have found the bottleneck that was troubling me :-) Regards, Brian. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs