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
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