AHA-2940UW, DLT, alpha & aic driver

[Metod Kozelj]

Hello,

On Wed, 1 Mar 2000, Doug Ledford wrote:

> > My problem real problem is, that 'mt -f /dev/nst0 fsf' doesn't do
> > anything.
> 
> In what context?  Several tape drives I've worked with in the past will accept
> the fsf command silently, seeming to do nothing, but if you actually tried to
> read or write to the tape after executing the command, then the drive does the
> reposition before the read or write.  In my experience, it works just fine. 
> Regardless though, this wouldn't be an aic7xxx driver problem, this would be a
> problem in the scsi tape driver (if it is even a problem).

Another member of this list suggested that this was a problem of mt,
shipped with RH5.1 and RH5.2. Upgrading to mt shipped with RH6.1 indeed
solved that problem.

Regarding your suggestion: if I do

mt -f /dev/nst0 fsf 1
tar -tvf /dev/nst0

it still acesses the first archive on tape. So it never actually performs
forward seek.

> > There's some funny thing about /proc/scsi/aic7xxx/0 contents: statisctics
> > for the DLT never change while statistics for disks do change.
> 
> The driver uses the cmd->request.cmd variable as the main indicator of whether
> the command is a read or a write command.  If the upper layer SCSI driver
> doesn't fill that variable in, then you see the behavior you are seeing. 
> Furthermore, we only track the transfer data on commands that actually use a
> command buffer, there are a number of commands, such as fsf, that don't
> trigger any sort of data length calculation in the driver.

So you are suggesting that even if I actually read the data from DLT
(using 'tar -tvf /dev/nst0'), it's just fine for stats not to reflect any
reads? And that this is st driver's failure?

Regards,
  Metod

Metod Kozelj

mailto:Metod.Kozelj at rzs-hm.si            /\  Ne posiljajte mi smeti ker grizem!
http://www.rzs-hm.si/                   /  \  Don't spam me for I bite!
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---- perl -e 'print $i=pack(c5,(41*2),sqrt(7056),(unpack(c,H)-2),oct(115),10);'




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