Date: Tue, 2 Apr 1996 11:03:28 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: luigi@labinfo.iet.unipi.it (Luigi Rizzo) Cc: davidg@Root.COM, dutchman@spase.nl, freebsd-hackers@freebsd.org Subject: Re: HDD cpu usage (IDE vs. SCSI). Message-ID: <199604020133.LAA08679@genesis.atrad.adelaide.edu.au> In-Reply-To: <199604011545.RAA23295@labinfo.iet.unipi.it> from "Luigi Rizzo" at Apr 1, 96 05:45:05 pm
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Luigi Rizzo stands accused of saying: > > > >How come the seagate uses twice as much cpu as the quantum? > > > > Because a Pentium-90 is much faster than a 486-100 for certain things and > > most of the %CPU is for total I/O overhead, not just the overhead in the > > device driver. > > Hmmm... if I get it right this means that under certain circumstances > (1 disk, onboard IDE controller, medium-fast CPU) using SCSI instead > of IDE gives you only a very little saving (which BTW is what I am > convinced of, but this has not been the dominating opinion on this > list). No, you're not understanding. For a given CPU, IDE will _always_ use more CPU time than SCSI. Period. If you have lots of free CPU, then IDE is fine, but if you feel that your CPU has better things to do with its time than copy data to and from your disk, then SCSI is the only solution that makes sense. > Luigi -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[
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