From owner-freebsd-hardware Thu May 1 15:18:15 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id PAA21099 for hardware-outgoing; Thu, 1 May 1997 15:18:15 -0700 (PDT) Received: from pluto.plutotech.com (root@pluto100.plutotech.com [206.168.67.137]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id PAA21094 for ; Thu, 1 May 1997 15:18:13 -0700 (PDT) Received: from narnia.plutotech.com (narnia.plutotech.com [206.168.67.130]) by pluto.plutotech.com (8.8.5/8.8.3) with ESMTP id QAA22846; Thu, 1 May 1997 16:17:55 -0600 (MDT) Message-Id: <199705012217.QAA22846@pluto.plutotech.com> X-Mailer: exmh version 2.0beta 12/23/96 To: "Jin Guojun[ITG]" cc: hardware@FreeBSD.ORG Subject: Re: 53C875 UW SCSI-3 adapter In-reply-to: Your message of "Thu, 01 May 1997 14:15:34 PDT." <199705012115.OAA10970@george.lbl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 01 May 1997 17:16:13 -0600 From: "Justin T. Gibbs" Sender: owner-hardware@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk >Under both 2.1.7 and 2.2.1, the 53C875 ultra-wide SCSI-III host adapter, made >by J Bond Computer Systems (JDC5075), has the same performance as the 53C825, >which is just a wide SCSI host adapter, about 18 MBytes/sec. >The disk drive I used are Seagate BARRACUDA 9 (ST19171W) , which seagate >claims that can go 40 MBytes in sychronous-transfer mode. > >Has someone experimented the throughput of 53C875 ultra-wide SCSI-III host >adapter with any wide or ultra-wide drives? > >-Jin If you only have a single drive on the bus, the difference between 20MB/s and 40MB/s transfer rates on the bus will not make much of a difference in your benchmarks. The bus is not your bottleneck. The media transfer rate is. There are very few drives that can transfer to/from the media at rates above 10MB/s. In fact, the fastest I've seen a Seagate 'Cuda (this was a 4gig drive) transfer into cache was 15MB/s on an ultra/narrow bus with no other devices on it. -- Justin T. Gibbs =========================================== FreeBSD: Turning PCs into workstations ===========================================