Date: 15 Oct 1999 10:26:41 +0300 From: Ville-Pertti Keinonen <will@iki.fi> To: parag@cgt.com (Parag Patel) Cc: freebsd-scsi@freebsd.org Subject: Re: Odd dmesg output or SCSI tagged-queueing problem? Message-ID: <86yad5jd8u.fsf@not.demophon.com> In-Reply-To: parag@cgt.com's message of "15 Oct 1999 09:17:39 %2B0300" References: <689.939968210@pinhead.parag.codegen.com>
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parag@cgt.com (Parag Patel) writes: > Now I seem to remember that these IBM drives used to be displayed like > the Quantum, that is with the string "Tagged Queueing Enabled". I > searched all the /var/log/messages files to see if any earlier kernel > did display this, but nothing up to 4.0-CURRENT as of May 1999 displayed > this string, and I've switched to running STABLE since. There's a comment in sys/cam/cam_xpt.c about the DCAS: { /* * Slow when tagged queueing is enabled. Write performance * steadily drops off with more and more concurrent * transactions. Best sequential write performance with * tagged queueing turned off and write caching turned on. * * PR: kern/10398 * Submitted by: Hideaki Okada <hokada@@isl.melco.co.jp> * Drive: DCAS-34330 w/ "S65A" firmware. * * The drive with the problem had the "S65A" firmware * revision, and has also been reported (by Stephen J. * Roznowski <sjr@@home.net>) for a drive with the "S61A" * firmware revision. * * Although no one has reported problems with the 2 gig * version of the DCAS drive, the assumption is that it * has the same problems as the 4 gig version. Therefore * this quirk entries disables tagged queueing for all * DCAS drives. */ { T_DIRECT, SIP_MEDIA_FIXED, "IBM", "DCAS*", "*" }, /*quirks*/0, /*mintags*/0, /*maxtags*/0 }, I didn't notice this until recently, either, even though the quirk entry has been there for a while. I'm not quite convinced that tagged queueing really hurts, but haven't bothered to do any testing. The DCAS isn't *that* fast, in any case (but other than in terms of performance, it seems very good). To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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