Date: Tue, 10 Jul 2001 13:32:02 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Stephen McKay <mckay@thehub.com.au> Cc: <freebsd-scsi@FreeBSD.ORG>, Norman Czarczinski <Norman.Czarczinski@t-online.de> Subject: Re: Trouble with SCSI Streamer Message-ID: <20010710132824.C99370-100000@wonky.feral.com> In-Reply-To: <200107101252.f6ACqMF26033@dungeon.home>
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On Tue, 10 Jul 2001, Stephen McKay wrote:
> On Wednesday, 4th July 2001, Matthew Jacob wrote:
>
> >On Wed, 4 Jul 2001, Norman Czarczinski wrote:
> >
> >> On Wednesday 04 July 2001 19:34, you wrote:
> >> > Well, that's one theory shot down. Can you explicitly try changing the
> >> > blocksize to 1k, test, back to 512 and test again?
> >>
> >> That was it. With 1k it works. After switching back to 512 the problem came
> >> back.
> >
> >Okay- sounds like a bug in sa(4) then- and wierdness in the drive. It
> >shouldn't allow you to set it to 512 bytes if that doesn't work.
>
> This is deja vu time! We had this discussion a couple of years ago,
> if I recall correctly. QIC tapes in fixed block mode at densities of
> QIC-320 and above are in 1k blocks, and below that they are 512 byte blocks.
> It is not linked to a drive type, but to the tape density.
>
> Instead of getting to the bottom of this and making the sa driver know
> everything there was to know about QIC drives, the resolution was to
> use variable length blocks on QIC-320 and above. At the time, I had
> some philosophical quibbles with this approach, but it seems quite
> practical in retrospect.
No, I don't agree. A lot of QIC tape drives don't get emulated (it has to be
emulated because they cannot actually *do* variable blocksize) blocksizes
right.
> Indeed, checking the pre-cam st driver reveals the default is as I just
> described. But checking the cam sa driver reveals quirks that set 1024
> byte fixed blocks on some drives, and more code that sets 512 byte
> blocks for lots of densities, including ones that it shouldn't. That's
> not right.
Yes, this probably is true. Currently, if this code is exercised (which is
rarer than it should be):
switch (softc->media_density) {
case SCSI_DENSITY_QIC_11_4TRK:
case SCSI_DENSITY_QIC_11_9TRK:
case SCSI_DENSITY_QIC_24:
case SCSI_DENSITY_QIC_120:
case SCSI_DENSITY_QIC_150:
case SCSI_DENSITY_QIC_525_320:
case SCSI_DENSITY_QIC_1320:
case SCSI_DENSITY_QIC_3080:
softc->quirks &= ~SA_QUIRK_2FM;
softc->quirks |= SA_QUIRK_FIXED|SA_QUIRK_1FM;
softc->last_media_blksize = 512;
break;
case SCSI_DENSITY_QIC_4GB:
case SCSI_DENSITY_QIC_2GB:
softc->quirks &= ~SA_QUIRK_2FM;
softc->quirks |= SA_QUIRK_FIXED|SA_QUIRK_1FM;
softc->last_media_blksize = 1024;
break;
This should probably be:
switch (softc->media_density) {
case SCSI_DENSITY_QIC_11_4TRK:
case SCSI_DENSITY_QIC_11_9TRK:
case SCSI_DENSITY_QIC_24:
case SCSI_DENSITY_QIC_120:
case SCSI_DENSITY_QIC_150:
softc->quirks &= ~SA_QUIRK_2FM;
softc->quirks |= SA_QUIRK_FIXED|SA_QUIRK_1FM;
softc->last_media_blksize = 512;
break;
case SCSI_DENSITY_QIC_525_320:
case SCSI_DENSITY_QIC_1320:
case SCSI_DENSITY_QIC_3080:
case SCSI_DENSITY_QIC_4GB:
case SCSI_DENSITY_QIC_2GB:
softc->quirks &= ~SA_QUIRK_2FM;
softc->quirks |= SA_QUIRK_FIXED|SA_QUIRK_1FM;
softc->last_media_blksize = 1024;
break;
It turns out, though, that this code path is rarely exercised because our
beloved QIC manufactures often just report 'default' density (0).
>
> I think a useful exercise would be to copy more of the QIC heuristics from
> the old st driver into the sa driver.
Got patches?
-matt
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