Date: Sun, 06 May 2001 17:00:39 +0200 From: Jean-Sebastien ROY <jean-sebastien.roy@wanadoo.fr> To: freebsd-stable@freebsd.org Subject: Re: Tagged Queueing and ATA driver (was soft update should be default) Message-ID: <jean-sebastien.roy-8A1B73.17003906052001@durandal.root> References: <00b601c0d5bd$42ba1340$0901a8c0@haym.transactionsite.com> <Pine.BSF.4.33.0105061425380.84550-100000@merlin.th.physik.uni-bonn.de>
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(Jan Conrad) wrote: > Well, if I read the sources correctly, enabling tagged queueuing in the > ata driver *IMPLIES* write caching!!! > > So it's pretty clear why tagged queueing is as good as write cacheing (or > as bad :-) > > sys/dev/ata/ata-disk.c of 4.3R says > > /* enable write cacheing if allowed and not default on device */ > if (ata_wc || ata_tags) { > if (ata_command(adp->controller, adp->unit, ATA_C_SETFEATURES, > 0, 0, 0, 0, ATA_C_F_ENAB_WCACHE, ATA_WAIT_INTR)) > ata_printf(scp, device, "enabling write cache failed\n"); > } > > What I really do not understand here - maybe it's trivial, as I am not an > expert here - is why does tags imply wc for ATA but not for SCSI? > > The SCSI driver says 'Tagged Queueing Enabled' even on my SCSI disk (IBM > DDYS-T18350N) where WCE is off! > > > -Jan On a related note, is there a way to know if Tagged Queueing and/or Write Caching are -really- enabled ? I've got a Promise controller (<Promise ATA100 controller>), and looking at the code, it seems "Tagged Queueing" is disabled on some promise controllers. But : systctl -a | grep ata always returns what I've put in /boot/loader.conf ie : hw.ata.tags: 1 js To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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