From owner-freebsd-scsi Sat Oct 16 12:47:13 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from feral.com (feral.com [192.67.166.1]) by hub.freebsd.org (Postfix) with ESMTP id 050511543D for ; Sat, 16 Oct 1999 12:47:09 -0700 (PDT) (envelope-from mjacob@feral.com) Received: from semuta.feral.com (semuta [192.67.166.70]) by feral.com (8.8.7/8.8.7) with ESMTP id MAA13390; Sat, 16 Oct 1999 12:46:57 -0700 Date: Sat, 16 Oct 1999 12:46:57 -0700 (PDT) From: Matthew Jacob Reply-To: mjacob@feral.com To: Gerard Roudier Cc: "Kenneth D. Merry" , "Chris D. Faulhaber" , Andrew Gallatin , scsi@FreeBSD.ORG Subject: Re: FreeBSD 3.2 / Slow SCSI Dell PowerEdge 4300 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > Hmmm... This can only happened with too old or poor designed SCSI > controllers. Well designed SCSI controllers do not interrupt uselessly. > About disabling SCSI disconnections, I would have been glad not to have > read that. Note that I am not going to ever choose a SUN originated > system for numerous reasons. ;-) I'm talking about 14 years ago, btw... So, before you slam Sun for this, remember it was pretty good for the time and price class. I would buy Suns *now*, but for other reasons and for certain properties that may popular OSS systems have no clue about yet. > > > I suspect that the right thing here is to to ultimately do completely > > adaptive scheduling with hints- this would also solve the arguments I > > May be, a simple but kind bug that add some mess-up to disksort would > solve the problem. :-) > > > constantly have with Matt Dillon over whether MAXPHYS is too small at > > 128KB (it most certainly is if you have a job mix that's mainly large > > sequential writes or reads)- but until that point, document the tools that > > allow you to tune things and tell users "Knock yerself out... have a great > > time!" > > I have measured 35MB/s throughtput on a 80MB/s LVD SCSI BUS using 4K > actual IO chunks. This let me think that 64 KB is not that small given not > ridiculouly high IO latency. May-be for Ultra-160 (and probably for future > Ultra-320), 64KB will be to small. Again- it depends. I doubt that it's the bus speed that makes this a fine thing here- it's very likely the faster microprocessors on the newer LVD disks. Fibre Channel disks have some of the same properties, but even better is the fact that non-data phases pretty much don't exist in fibre channel, so there's no such thing as blowing through a 4k data phase at 40Mhz+ only to sit and pick your nose for hundreds of microseconds for status and message in and bus settle delay and arb delay..... -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message