Date: Mon, 17 Jan 2000 14:44:45 +0100 (CET) From: Micke Josefsson <mj@isy.liu.se> To: "Kenneth D. Merry" <ken@kdm.org> Cc: freebsd-questions@FreeBSD.ORG, Rick Hamell <hamellr@aracnet.com> Subject: Re: Expected SCSI speed question Message-ID: <XFMail.000117144445.mj@isy.liu.se> In-Reply-To: <20000116012238.A30815@panzer.kdm.org>
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On 16-Jan-00 Kenneth D. Merry wrote: > 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. Apparently! That gave some 3.5Meg/second. Without the bs=1m stuff it peaked around 660 k/sec. Surprisingly similar to what a file to /dev/null runs at. Perhaps there is no problem at all then! Sure made me happy! Thanks for your help! /Micke ---------------------------------- Michael Josefsson, MSEE mj@isy.liu.se This message was sent by XFMail running on FreeBSD 3.1 ---------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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