Andy Corteen and Martin Jacobs answered to my question regarding the
"overrun error" of ditto max stating that these errors cannot be prevented
because of various items.
Now, don't you think that a real alternative to junk the ditto max could be
to patch the ftape code in order to let it deals also with speeds lower than
2Mb/s? If we were able to drive the to the streamer at 1Mb/s, I think that
the global speed factor would be enhanced, because of the reduced
number of retry due to overrun.
In fact, 1Mbit/s means more than 7.5 Mbytes/minute that is almost three
times the rate I measured using a theoretical 2Mbit/s setting.
Actually, if I set the parameter ft_fdc_rate_limit to 1000, the drive won't
be recognized nor run. Do someone knows how to modify the software in order
to let this value to be accepted?
Another way to follow could be to connect the streamer directly to the
standard floppy interface, thus avoiding the use of the EZ board, but also
this seems not to be running.
In any case, there is the need of a patch.
If the question is of general interest, I hope that someone that known the
behaviour of ftape software can help me (an someone else, too!)
Thank you
Fabio Lissandini
----- Original Message -----
From: Fabio Lissandrini <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, November 29, 1999 10:36 AM
Subject: Overrun errors
> After a few trial, I've been able to drive my ditto max with the Sept 11th
> version (unstable) of ftape.
> Now, I observe that the speed is very slow. I got, on the average, about
> 2Mbytes/minute: this means that, for a backup that is expected to fill a
5MB
> tape, it will be necessary more than 41 hours!!! This fact seems strange.
> So, I had a look at the system log, and I saw that very often there is an
> "overrun error" followed by a retry that writes ok. Each overrun is
> accompanied by a audible tape rewind of about a few 100ms. It's obvious
that
> such a lot of mechanical rewinds increases the total time needed for a
> backup, so slowing down the entire process.
>
> I made a trial on the same pc, booted with dos, running the "ditto tools"
> program furnished by Iomega. Doing a backup with this, there is no audible
> rewinds, and the backup completes at a speed that is not revolutionary,
but
> is almost three times faster than the linux trial.
>
> So, it's clear to me that the problem is not hardware. The documentation
> states that in order to avoid overruns, the parameter ft_fdc_threshold
> should be put at 15. But this doesn't bring to any improvement.
>
> Is there a way to avoid the overruns?
>
> P.S. the configuration of the EZ board is quite correct. The same
io/irq/dma
> found by isapnp has been used for the ftape initialization; they are not
> used by another application; the ft_fdc_threshold is 15.
>
> Thank you in advance.
> Fabio Lissandrini
>
>
