Date: Thu, 30 Aug 2007 06:57:36 -0600 From: Scott Long <scottl@samsco.org> To: "Lutieri G." <lutierigbtrabalho@gmail.com> Cc: FREEBSD - SCSI - LIST <freebsd-scsi@freebsd.org> Subject: Re: performance with LSI SAS 1064 Message-ID: <46D6BEC0.1050104@samsco.org> In-Reply-To: <71d0ebb0708300502x632fe83bo617f84ca2008dc7d@mail.gmail.com> References: <71d0ebb0708291245g79d2141fx73cc8a6e76875944@mail.gmail.com> <46D5E17F.3070403@samsco.org> <71d0ebb0708291416v17351c65u7ccc1b7bbe0271d2@mail.gmail.com> <46D5E5B1.207@samsco.org> <71d0ebb0708291506i49649a60l8006deafb20891ac@mail.gmail.com> <46D63710.1020103@freebsd.org> <71d0ebb0708300502x632fe83bo617f84ca2008dc7d@mail.gmail.com>
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Lutieri G. wrote: > 2007/8/30, Eric Anderson <anderson@freebsd.org>: >> I'm confused - you said in your first post you were getting 3MB/s, where >> above you show something like 55MB/s. > Sorry! using blogbench i got 3MB/s and 100% busy. Once is 100% busy i > thinked that 3MB/s is the maximum speed. But i was wrong... %busy is a completely useless number for a anything but untagged, uncached disk subsystems. It's only an indirect measure of latency, and there are better tools for measuring latency (gstat). >> You didn't say what kind of disks, or how many, the configuration, etc - >> so it's hard to answer much. The 55MB/s seems pretty decent for many >> hard drives in a sequential use state (which is what dd tests really). >> > SAS disks. Seagate, i don't know what is the right model of disks. > > Ok. If 55Mb/s is a decent speed i'm happy. I'm getting problems with > squid cache and maybe should be a problem related with disks. But... > i'm investigating and discharging problems. > > >> Your errors before were probably caused because your queue depth is set >> to 255 (or 256?) and the adapter can't do that many. You should use >> camcontrol to reduce it, to maybe 32. See the camcontrol man page for >> the right usage. It's something that needs setting on every boot, so a >> startup file is a good place for it maybe. >> > Is there any way of get the right number to reduce?! > If you're seeing erratic performance in production _AND_ you're seeing lots of accompanying messages on the console about tag depth jumping around, you can use camcontrol to force the depth to a lower number of you're choosing. This kind of problem is pretty rare, though. Scott
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