From owner-freebsd-stable Thu Jun 25 08:49:44 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id IAA29863 for freebsd-stable-outgoing; Thu, 25 Jun 1998 08:49:44 -0700 (PDT) (envelope-from owner-freebsd-stable@FreeBSD.ORG) Received: from polaris.we.lc.ehu.es (polaris.we.lc.ehu.es [158.227.6.43]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id IAA29848 for ; Thu, 25 Jun 1998 08:49:36 -0700 (PDT) (envelope-from jose@we.lc.ehu.es) Received: from we.lc.ehu.es by polaris.we.lc.ehu.es (SMI-8.6/SMI-SVR4) id RAA04333; Thu, 25 Jun 1998 17:45:55 +0200 Message-ID: <359270B2.B1BF0D23@we.lc.ehu.es> Date: Thu, 25 Jun 1998 17:45:54 +0200 From: "Jose M. Alcaide" Organization: Universidad del País Vasco - Dept. Electricidad y Electrónica X-Mailer: Mozilla 4.05 [en] (X11; I; FreeBSD 2.2.6-STABLE i386) MIME-Version: 1.0 To: bm@malepartus.de CC: freebsd-stable@FreeBSD.ORG Subject: Re: SCSI; tagged command queuing References: <199806251229.OAA22711@Reineke.Malepartus.de> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Burkard Meyendriesch wrote: > I'm running FreeBSD (2.2-stable) on an ASUS-Motherboard (K6/233Mhz) with > onboard SCSI controller "Adaptec aic7880 Ultra SCSI host adapter" driven > by "ahc0" device driver. I'm operating a couple of SCSI devices (tapes, > disks, CDs) on the SCSI bus. My experience is that using a tape slows > down the disk I/O significantly. So I decided to use "tagged command > queuing". (Yes, I did read the comments on this in the generig config > file "/usr/src/sys/i386/conf/LINT". ;-) ) > Mmmm... I don't see clearly why TCQ should improve disk I/O when using the tape. In any case, probably the tape drive does not support TCQ. Boot -v, and see the messages from the AHC driver. You should see "ahc0: target N Tagged Queing Device" for each SCSI device that supports TCQ. I don't know why tape I/O slows down disk I/O. Start SCSISelect at boot, and check that the SCSI disconnect/reconnect feature is enabled. However, this is useful only if the tape drive supports this feature. -- JM ----------------------------------------------------------------------- Jose M. Alcaide | mailto:jose@we.lc.ehu.es Universidad del Pais Vasco | http://www.we.lc.ehu.es/~jose Dpto. de Electricidad y Electronica | Facultad de Ciencias - Campus de Lejona | Tel.: +34-944647700 x2624 48940 Lejona (Vizcaya) - SPAIN | Fax: +34-944858139 ----------------------------------------------------------------------- "Go ahead... make my day." - H. Callahan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message