Date: Fri, 13 Aug 2010 20:47:15 -0700 From: "Kevin Oberman" <oberman@es.net> To: TJ Varghese <tj@tjvarghese.com> Cc: Roland Smith <rsmith@xs4all.nl>, stable@freebsd.org Subject: Re: Inconsistent IO performance Message-ID: <20100814034715.09FE21CC3A@ptavv.es.net> In-Reply-To: Your message of "Sat, 14 Aug 2010 11:06:58 %2B0800." <AANLkTikkHfwHZAWA35iAG83Pxp4nv2cjhOUd5wMVxsXb@mail.gmail.com>
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> Date: Sat, 14 Aug 2010 11:06:58 +0800 > From: TJ Varghese <tj@tjvarghese.com> > > > > > > > Maybe there is a hardware component here? Are both disks on the same > > > controller? Or if not are both controllers using the same interrupt line? > > > > No. Each is on its one controller and is the only disk on that > > controller. > > > > > You should have a look at 'systat -vmstat' with dd running in the > > > background. That might give a clue as to where the bottleneck is. > > > > > > > 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. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
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