Date: Wed, 12 Jun 1996 11:38:20 -0400 (EDT) From: David Miller <isdmill@gatekeeper.ddp.state.me.us> To: "Jacob M. Parnas" <jparnas@jparnas.cybercom.net> Cc: Bob Loftus <bobster@primenet.com>, "Aaron D. Gifford" <agifford@infowest.com>, freebsd-questions@freebsd.org, bsdi-users@BSDI.COM Subject: Re: Adaptec2940UW vs. BusLogicBT-958 (opinions?) Message-ID: <Pine.BSI.3.93.960612112905.8030B-100000@gatekeeper.ddp.state.me.us> In-Reply-To: <199606121235.IAA12473@jparnas.cybercom.net>
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On Wed, 12 Jun 1996, Jacob M. Parnas wrote: > In message <Pine.BSD.3.91.960611162414.19152A-100000@usr06.primenet.com>you write: > >I believe that Paul Vixie has expounded quite masterfully on this topic > >in the past, check the bsdi-users archive @ nexial.nl as I recall it > >doesn't really matter, and you can't possibly keep the scsi bus busy > >enough to warrant it. "Wide SCSI is just for those suffering from > >spec-envy." "Wide SCSI has lovely marketing, I guess. Everybody wants it, > >nobody needs it." -- Paul Vixie > >Have fun... > > Would you please elaborate a bit on the logic? I don't see why with up to > 15 devices, you couldn't fill up 40MB/sec for a fast/wide/ultra SCSI III bus? > Especially with some raids counting as one large SCSI device? It's not too hard to conceive of hardware which would fill > 10 MB/s. But the application is another matter. If you want to strip real time uncompressed video, you probably need it. If you're in the lab and need to do some kind of data acquisition you might need it. But running a busy web/news/mail/other-inet-application server doesn't - it needs lots of ios/sec, not lots of bandwidth. And a fast scsi channel can request just as many random seeks/sec as a UW bus. Again I'll challenge people to run iozone against either a MFS (am based) file system or just small files which fit within the disk cache system. If you can only write to *ram* at 10-20 MB/sec do you think it'll write to a scsi (UW) channel any faster? When the PC's your UW controller is in are enough faster, and or the bsdi/freebsd developers have refined the IO subsystems enough that a scsi channel is a fundamental limitation, then I'll be a proponent of UW - or whatever the current high speed spec is:) --- David Miller ---------------------------------------------------------------------------- It's *amazing* what one can accomplish when one doesn't know what one can't do!
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