Date: Sun, 16 Jan 2000 01:22:38 -0700 From: "Kenneth D. Merry" <ken@kdm.org> To: Rick Hamell <hamellr@aracnet.com> Cc: Micke Josefsson <mj@isy.liu.se>, freebsd-questions@FreeBSD.ORG Subject: Re: Expected SCSI speed question Message-ID: <20000116012238.A30815@panzer.kdm.org> In-Reply-To: <Pine.LNX.4.10.10001141421540.11522-100000@shell1.aracnet.com>; from hamellr@aracnet.com on Fri, Jan 14, 2000 at 02:25:17PM -0800 References: <XFMail.000114094500.mj@isy.liu.se> <Pine.LNX.4.10.10001141421540.11522-100000@shell1.aracnet.com>
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On Fri, Jan 14, 2000 at 14:25:17 -0800, Rick Hamell wrote: > > > I have a 200 MHz K6 system (FBSD 3.2), Adaptec 2940UW SCSI-adaptor and Seagate > > ST19171W Hard disk. The Seagate (Barracuda 9) disk is specced to up to 40 > > Mbytes/sec Max sync. SCSI transfer rate. But whatever tests I run (copying > > large files to and fro, dd from disk to /dev/null for example) the actual speed > > is never more than around 0.5 MB/s according to 'systat -io 1' or 'systat -vm > > 1'. > > > > Is there a knob to turn to speed it up or is this a bottleneck due to the > > processor? > > I've noticed that the Adaptec 2940UW seems to be a fairly slow > card, at this point I'm pulling every single one I come across and > replacing with Tekram cards. The biggest differance I saw was doing a > drive mirror under Novell 3.12 a couple of weeks ago. Dual 2940s with > their own seperate drives took 3 hours. Using the exact same model drive > and two of the Tekram cards took under 20 minutes. Under FreeBSD I've seen > similar performance. :( That certainly hasn't been my experience. The only thing I can figure is that you've got things misconfigured somehow. Your problem under Novell is likely a driver issue of some sort. I'm sure the Tekram cards will perform fine, assuming you get NCR/Symbios based boards. Make sure you use the 'sym' driver, since the 'ncr' driver is fairly buggy, and somewhat lacking in the error recovery department. The original poster's speed problems are due to the speed of the drive, and have nothing to do with the controller. Just because a drive's bus speed is 40MB/sec doesn't mean the heads/media can push the bits that fast. The Barracuda 9 is a fairly old drive, but I would think it would be able to do more than 5MB/sec. To test it out, try something like this: dd if=/dev/rda0 of=/dev/null bs=1m count=2048 You have to make the blocksize big enough in order to get any performance. Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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