Date: Mon, 8 May 1995 15:34:11 -0700 (PDT) From: Tom Samplonius <tom@haven.uniserve.com> To: Scott Mace <smace@metal-mail.neosoft.com> Cc: hackers@FreeBSD.org Subject: Re: Is a 486 fast enough for SCSI? Message-ID: <Pine.BSF.3.91.950508152847.717C-100000@haven.uniserve.com> In-Reply-To: <199505082158.PAA00426@metal.ops.neosoft.com>
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On Mon, 8 May 1995, Scott Mace wrote: > > I've got a AMD486DX4100 with an Adaptec 2940 and two SCSI drives. When > > I run iozone on one drive I get about 1.9MB/s, but when I run a iozone on > > each drive I get about .9 MB/s (roughly half). Since the SCSI bus runs > > at 10MB/s per second, the limiting factor appears to be the CPU? I > > thought PCI devices required very little CPU time? > > > > The limiting time is the speed of the drive. I can get over 3megs/sec > with my EISA bt747 and seagate barracuda drives. And my cpu is only > a 486DX2-66. I'm never seen a single scsi drive actually do 10MB/sec. I realize that no SCSI drive can do 10MB/s, but it is clearly not the bottleneck when accessing two drives simultaneously, so what is? Tom
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