From owner-freebsd-hackers Sun Oct 8 15:12:08 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id PAA13694 for hackers-outgoing; Sun, 8 Oct 1995 15:12:08 -0700 Received: from kryten.atinc.com (kryten.Atinc.COM [198.138.38.7]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id PAA13689 for ; Sun, 8 Oct 1995 15:12:05 -0700 Received: (jmb@localhost) by kryten.atinc.com (8.6.9/8.3) id SAA28462; Sun, 8 Oct 1995 18:01:36 -0400 Date: Sun, 8 Oct 1995 18:01:35 -0400 (EDT) From: "Jonathan M. Bresler" Subject: Re: VLB Disk Controllers To: Bruce Evans cc: julian@ref.tfs.com, roberto@keltia.freenix.fr, bde@zeta.org.au, dennis@etinc.com, hackers@freebsd.org In-Reply-To: <199510082145.HAA11073@godzilla.zeta.org.au> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-hackers@freebsd.org Precedence: bulk On Mon, 9 Oct 1995, Bruce Evans wrote: > >> > transfer speed is 1.25286e+07 bytes/sec > > >heh? > >how do you get 12MB/sec on a 10MB/sec SCSI bus? well how about these numbers (dont sweat them, i have not yet created the sd1sX devices) ./disklatency /dev/rsd1f Command overhead is 11092 usec (time_4096 = 11098, time_8192 = 11104) transfer speed is 6.88982e+08 bytes/sec Aspen: {258} !! ./disklatency /dev/rsd1f Command overhead is 6270 usec (time_4096 = 4104, time_8192 = 1938) transfer speed is -1.891e+06 bytes/sec Aspen: {259} !! ./disklatency /dev/rsd1f Command overhead is 10991 usec (time_4096 = 11098, time_8192 = 11204) transfer speed is 3.84637e+07 bytes/sec Aspen: {260} !! ./disklatency /dev/rsd1f Command overhead is 11065 usec (time_4096 = 11120, time_8192 = 11175) transfer speed is 7.4424e+07 bytes/sec > > It's the relative transfer speed for transferring 4K blocks and 8K > blocks. If 4K blocks are transferred at 5MB/sec and 8K blocks are > transferred at 10MB/sec, then the relative speed is infinite :-). > This shows that the test is biased. It prints the speed mainly as > a sanity test. If the speed isn't close to the SCSI bus speed, then > you shouldn't trust any of the results of the test. > > Bruce > Jonathan M. Bresler jmb@kryten.atinc.com | Analysis & Technology, Inc. FreeBSD Postmaster jmb@FreeBSD.Org | 2341 Jeff Davis Hwy play go. | Arlington, VA 22202 ride bike. hack FreeBSD.--ah the good life | 703-418-2800 x346