Date: Thu, 25 Jun 1998 17:45:54 +0200 From: "Jose M. Alcaide" <jose@we.lc.ehu.es> To: bm@malepartus.de Cc: freebsd-stable@FreeBSD.ORG Subject: Re: SCSI; tagged command queuing Message-ID: <359270B2.B1BF0D23@we.lc.ehu.es> References: <199806251229.OAA22711@Reineke.Malepartus.de>
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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
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