From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Landman Subject: Re: high throughput storage server? Date: Thu, 24 Feb 2011 16:07:50 -0500 Message-ID: <4D66C8A6.7030600@gmail.com> References: <4D5A7198.7060607@hardwarefreak.com> <4D66C55F.2050003@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D66C55F.2050003@gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Zdenek Kaspar Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 02/24/2011 03:53 PM, Zdenek Kaspar wrote: >> And likewise, what if there are three clients, or four clients, ..., >> all requesting different but large files simultaneously? >> >> How does one calculate the drive's throughput in these cases? And, >> clearly, there are two throughputs, one from the clients' >> perspectives, and one from the drive's perspective. we us Jens Axboe's fio code to model this. Best case scenario is you get 1/N of the fixed sized resource that you share averaged out over time for N requestors of equal size/priority. Reality is often different, in that there are multiple stacks to traverse, potential seek time issues as well as network contention issues, interrupt and general OS "jitter", etc. That is, all the standard HPC issues you get for compute/analysis nodes, you get for this. Best advise is "go wide". As many spindles as possible. If you are read bound (large block streaming IO), then RAID6 is good, and many of them joined into a parallel file system (ala GlusterFS, FhGFS, MooseFS, OrangeFS, ... ) is even better. Well, as long as the baseline hardware is fast to begin with. We do not recommend a single drive per server, turns out to be a terrible way to aggregate bandwidth in practice. Its better to build really fast units, and go "wide" with them. Which is, curiously, what we do with our siCluster boxen. MD raid should be fine for you. Regards, Joe -- Joseph Landman, Ph.D Founder and CEO Scalable Informatics Inc. email: landman@scalableinformatics.com web : http://scalableinformatics.com http://scalableinformatics.com/sicluster phone: +1 734 786 8423 x121 fax : +1 866 888 3112 cell : +1 734 612 4615