Date: Sat, 14 Aug 2010 13:17:44 +0200 From: Pieter de Goeje <pieter@degoeje.nl> To: freebsd-stable@freebsd.org Cc: stable@freebsd.org, TJ Varghese <tj@tjvarghese.com>, Jeremy Chadwick <freebsd@jdc.parodius.com> Subject: Re: Inconsistent IO performance Message-ID: <201008141317.45174.pieter@degoeje.nl> In-Reply-To: <20100814035751.3436F1CC3B@ptavv.es.net> References: <20100814035751.3436F1CC3B@ptavv.es.net>
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On Saturday 14 August 2010 05:57:51 Kevin Oberman wrote: > > Date: Sat, 14 Aug 2010 11:33:57 +0800 > > From: TJ Varghese <tj@tjvarghese.com> > > > > > The deviation in your disk I/O isn't a major surprise (to me anyway), > > > given the system specs. What *does* surprise me is your abysmal I/O > > > speeds in general. 18MB/sec min, 24MB/sec max?! ICH6-M can do a lot > > > more than that. Something isn't right. > > > > it's possible that the hw is...suboptimal. From a 2005 post, > > > > http://forum.thinkpads.com/viewtopic.php?f=2&t=13036&start=0 > > > > Check out the link to the hddbenchmark, > > http://img57.imageshack.us/img57/6430/hddbenchmark1no.jpg > > Thanks, TJ! I guess the disk IO on these boxes simply sucks. Looks like > the 34.75MB/sec sequential read speed is all I can hope for. I'm > guessing the SATA-PATA converter is to blame. Oh, well. > > But all of this does not address my real question, why is performance so > inconsistent? I agree that it sucks, but that does not explain why it > suck so much worse on one run than another. I'm still baffled. > > My backup disk normally odes not leave my office storage cabinet except > when it is in the computer being written, so I don't have it handy > ATM. I will try a couple of things on Monday, though. Perhaps the measurements are taken while the laptop is on a different (less/more stable) surface each time? Disk vibrations could account for the differences. Check out this cool video from Sun: http://news.cnet.com/8301-13556_3-10138666-61.html No idea how this affects sequential read and write workloads however. -- Pieter de Goeje
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