Date: Sat, 14 Aug 2010 17:31:20 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Kevin Oberman <oberman@es.net> Cc: Roland Smith <rsmith@xs4all.nl>, stable@freebsd.org, TJ Varghese <tj@tjvarghese.com> Subject: Re: Inconsistent IO performance Message-ID: <20100814162034.I77596@sola.nimnet.asn.au> In-Reply-To: <20100814034715.09FE21CC3A@ptavv.es.net> References: <20100814034715.09FE21CC3A@ptavv.es.net>
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On Fri, 13 Aug 2010, Kevin Oberman wrote: > > Date: Sat, 14 Aug 2010 11:06:58 +0800 > > From: TJ Varghese <tj@tjvarghese.com> [..] > > You're using a laptop with 2 HDDs, so does that mean you're using the > > Ultrabay for the 2nd HDD? > > Perhaps anything connected to that drops down to ATA33 (pure speculation on > > my part) since it was designed for optical drives ...dmesg/atacontrol logs > > would be useful here. > > > > You may want to try dd with the of=/dev/null instead to remove the 2nd > > variable and benchmark solely the read speed of the 1st hdd. > > For this test I get a very consistent 34.75 MB. (1000 10M > blocks). Distressingly low when there is almost no seek activity. > > Nope, it is running at UDMA100 using a SATA-PATA converter. (The ICH6 > controller is SATA.) But that was a good idea. For some sort of comparison, on a T23 (1133MHz P3-M, ICH3 PATA, Fujitsu MHV2120AH 120GB 5400rpm UDMA100 drive, single device on channel, 768MB RAM), I do better than that: # dd if=/dev/ad0 of=/dev/null count=1024 bs=10M gets, over two runs, just either side of 40,500,000 bytes/s. Same result, just slightly better, with bs=512M count=20. (I also tried bs=1024M count=10, but that was really dumb with 768MB RAM :) But with if=/dev/ad0s4 (starts about 70% into the disk) just either side of 29,200,000 bytes/s. All tests show 0.5-0.7% CPU, so hardly a factor, and with that usage powerd kept the CPU at 733MHz. Could be as you suggest, the SATA to PATA converter is a bottleneck? I see mine has acoustic management on also; let us know if it matters? Oh, and that's on 8.0R, about to be brought up to 8.1-S, if relevant. cheers, Ian
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