From owner-freebsd-scsi Wed Feb 18 15:19:05 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA07961 for freebsd-scsi-outgoing; Wed, 18 Feb 1998 15:19:05 -0800 (PST) (envelope-from owner-freebsd-scsi@FreeBSD.ORG) Received: from pluto.plutotech.com (mail.plutotech.com [206.168.67.137]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA07940 for ; Wed, 18 Feb 1998 15:18:59 -0800 (PST) (envelope-from gibbs@plutotech.com) Received: from narnia.plutotech.com (narnia.plutotech.com [206.168.67.130]) by pluto.plutotech.com (8.8.7/8.8.5) with ESMTP id QAA01242; Wed, 18 Feb 1998 16:18:25 -0700 (MST) Message-Id: <199802182318.QAA01242@pluto.plutotech.com> X-Mailer: exmh version 2.0.1 12/23/97 To: Tom cc: "Justin T. Gibbs" , Wee Teck Ng , freebsd-scsi@FreeBSD.ORG Subject: Re: very slow scsi performance In-reply-to: Your message of "Wed, 18 Feb 1998 14:21:54 PST." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 18 Feb 1998 16:15:35 -0700 From: "Justin T. Gibbs" Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > Didn't the IBM DCAS or DORS drive have some firmware bugs in regards to >tags? Are you referrring to the newer IBM Ultrastar line? The problems that have been reported against many IBM drives stem from the fact that the DQUE bit is set on many OEM models. The current SCSI system does not look at the control mode page to see this, attempts to perform tagged queuing operation anyway, and fails miserably. The IBM drives are behaving completely within the bounds of the SCSI spec. CAM handles this "problem" by honoring the DQUE bit assuming that the user knows what they are doing. > In fact, I just found a message from a DCAS sent to a freebsd list >today, that has to disable disconnection to get reliable operation with >his 2940 and his DCAS drive. It is probably the same problem I listed above. Disabling disconnection effectively prevents tags from being used. >I can't verify that, but I have few problems >with 11 Seagate drives hung off a 3940UW. The ahc driver freezes up the >system every 6 weeks of heavy 24x7 i/o though. I'm working on finishing up this 7890 support so that I can release an updated CAM snapshot. Once that happens, you might want to try CAM and see if it addresses this problem. >Tom -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message