From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Heflin Subject: Re: southbridge/sata controller performance? Date: Sat, 03 Jan 2009 14:11:38 -0600 Message-ID: <495FC67A.2030201@gmail.com> References: <20090103193429.GA17462@sewage.raw-sewage.fake> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090103193429.GA17462@sewage.raw-sewage.fake> Sender: linux-raid-owner@vger.kernel.org To: Matt Garman Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Matt Garman wrote: > When using Linux software RAID, I was thinking that, from a > performance perspective, the southbridge/SATA controller is probably > one of the most important components (assuming a reasonable CPU). > Is this a correct generalization? > > If it is, has anyone done a study or benchmarked SATA controller > performance? Particularly with consumer-grade hardware? > > I haven't been able to find much info about this on the web; the > Tech Report seems to consistently benchmark SATA performance: > > AMD SB600: http://techreport.com/articles.x/13832/5 > AMD SB700: http://techreport.com/articles.x/14261/10 > AMD SB750: http://techreport.com/articles.x/13628/9 > Intel ICH10: http://techreport.com/articles.x/15653/9 > nVidia GeForce 8300: http://techreport.com/articles.x/14993/9 In general those benchmarks are mostly useless for Raid. The biggest different for RAID is what happens when multiple channels are used. On full speed streaming read/write almost every (even the worst PCI controllers on a PCI bus) sata controller is close to equal when you only have one drive, once you use 2 drives or more things change. If the given controller setup can actually run several drives at close to full single drive speed performance will be good, if it cannot things are going to get much slower. One test I do is a single dd from one disk and watch the io speed, and then I add dd's and watch what happens. I have 4 identical disks, 2 are on a ICH7, 2 are on a pci bus based MB controller, any single of these disks will do about 75MB/second no matter were it is, using 2 on the ich7 gets about 140-150MB/second, using the 2 on the pci bus based MB controller gets 98MB/second. If all of the controllers techreports tested were equal on this test, then it might be worth it to look at the benchmarks techreport is using, but the simple dd benchmark is likely more important, and I am pretty sure that someone could use a controller (on a bandwidth limited bus) that would do good on the above techreport benchmark, but fail horribly when several disks with a high io speed were being used and work badly for raid.