From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q149x69u202908 for ; Sat, 4 Feb 2012 03:59:06 -0600 Received: from greer.hardwarefreak.com (mo-65-41-216-221.sta.embarqhsd.net [65.41.216.221]) by cuda.sgi.com with ESMTP id Gnet1msl3gPfJEzl for ; Sat, 04 Feb 2012 01:59:05 -0800 (PST) Message-ID: <4F2D016C.9020406@hardwarefreak.com> Date: Sat, 04 Feb 2012 03:59:08 -0600 From: Stan Hoeppner MIME-Version: 1.0 Subject: Re: Performance problem - reads slower than writes References: <20120130220019.GA45782@nsrc.org> <20120131020508.GF9090@dastard> <20120131103126.GA46170@nsrc.org> <20120131145205.GA6607@infradead.org> <20120203115434.GA649@nsrc.org> <4F2C38BE.2010002@hardwarefreak.com> <20120203221015.GA2675@nsrc.org> In-Reply-To: <20120203221015.GA2675@nsrc.org> Reply-To: stan@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: Brian Candler Cc: Christoph Hellwig , xfs@oss.sgi.com On 2/3/2012 4:10 PM, Brian Candler wrote: > 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. Wow, you're right. How did I miss so many zeros? Got in hurry I guess. > 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. SSDs would fulfill criteria 1/2 but obviously not 3/4. > 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 :-) Will you be using mdraid or hardware RAID across those 24 spindles? -- Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs