Date: Sat, 16 Oct 1999 12:46:57 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Gerard Roudier <groudier@club-internet.fr> Cc: "Kenneth D. Merry" <ken@kdm.org>, "Chris D. Faulhaber" <cdf.lists@fxp.org>, Andrew Gallatin <gallatin@cs.duke.edu>, scsi@FreeBSD.ORG Subject: Re: FreeBSD 3.2 / Slow SCSI Dell PowerEdge 4300 Message-ID: <Pine.BSF.4.05.9910161238340.11481-100000@semuta.feral.com> In-Reply-To: <Pine.LNX.3.95.991016211142.659A-100000@localhost>
next in thread | previous in thread | raw e-mail | index | archive | help
> 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.4.05.9910161238340.11481-100000>