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To: se@ZPR.Uni-Koeln.DE (Stefan Esser)
cc: "Kenneth D. Merry" <ken@rflab1.gtri.gatech.edu>, hackers@freebsd.org
Subject: Re: VLB Disk Controllers 
In-reply-to: Your message of "Sun, 08 Oct 1995 00:35:34 BST."
             <199510072335.AA14520@Sysiphos> 
Date: Sat, 07 Oct 1995 17:22:10 -0700
From: "Justin T. Gibbs" <gibbs@freefall.FreeBSD.org>
Sender: owner-hackers@freebsd.org
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>On Oct 7, 19:13, "Kenneth D. Merry" wrote:
>} Subject: Re: VLB Disk Controllers
>
>} Adaptec 2842 on a i486DX4/100 VLB (QUANTUM XP34300) (Atlas, fast disk)
>} output for disklatency /dev/rsd0:
>} Command overhead is 567 usec (time_4096 = 1002, time_8192 = 1438)
>} transfer speed is 9.40748e+06 bytes/sec
>
>Well, you beat me, though not by much :)

The important thing is that we have support for enough controllers
in FreeBSD that we can actually bicker about which is faster. :)

>Something I just noticed is the big difference 
>in results I get using /dev/rsd0 vs. /dev/rsd0a:
>
># disklatency /dev/rsd0
>Command overhead is 719 usec (time_4096 = 1198, time_8192 = 1677)
>transfer speed is 8.55617e+06 bytes/sec
>
># disklatency /dev/rsd0a
>Command overhead is 807 usec (time_4096 = 1272, time_8192 = 1738)
>transfer speed is 8.80588e+06 bytes/sec
>
>Any ideas ???

Slice code?  It may be that we take some steps to validate the disklable
for that partition, do additional range checks etc.  Bruce probably
knows.

>STefan
>
>-- 
> Stefan Esser, Zentrum fuer Paralleles Rechnen		Tel:	+49 221 4706021
> Universitaet zu Koeln, Weyertal 80, 50931 Koeln	FAX:	+49 221 4705160
> =============================================================================
>=
> http://www.zpr.uni-koeln.de/staff/esser/esser.html	  <se@ZPR.Uni-Koeln.DE>

--
Justin T. Gibbs
===========================================
  Software Developer - Walnut Creek CDROM
  FreeBSD: Turning PCs into workstations
===========================================