Date: Fri, 27 Aug 1999 13:43:33 -0700 From: David Greenman <dg@root.com> To: chas <panda@skinnyhippo.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: how can you tell when disk i/o is limiting performance ? Message-ID: <199908272043.NAA06339@implode.root.com> In-Reply-To: Your message of "Sat, 28 Aug 1999 04:56:14 %2B0900." <3.0.5.32.19990828045614.00a07d80@mail.skinnyhippo.com>
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>Is there any method to measure disk I/O, in particular to >work out if it is limiting performance ? > >Context : >1 x 18 GB SCSI HD (10,000 RPM) > >Each day : >200,000 x CGI processes, each reading 2 or 3 flat files >100,000 x CGI processes, each reading/writing to mysql database >1,000,000+ x flat files (images, .html etc) > >plus 400 MB+ of apache log files are created each day. > >There seems to be ample RAM and CPU (and we're not even going >into swap) but the website is really crawling. I realise that >this could be due to the poor bandwidth in China (where the >server is hosted) but would like to also monitor the disk i/o >if it's possible since the CGIs open a lot of files and the apache >log files are being written nonstop. > >Hopefully then I can plan/budget for more disks and/or a second >server as traffic reaches a threshold. > >So : >a) can this be measured ? (i.e how do you know when your disk i/o is > the limiting factor ? ) Use "systat -iostat". Look at the TPS rates for each disk drive. Modern disk drives top out at around 80-120 TPS. >b) would it make more sense to have 3 separate (physical) disks for : > - apache log files > - mysql database > - operating system, applications, website files/cgi Yes, more disks is better. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org Creator of high-performance Internet servers - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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