Hi Fabio,
> 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?
Maybe. It's known that floppy tape drives at high speed
under a real multiuser environment may be critical in terms of
timing and bandwidth. Because FTAPE has to feed data in time
it has to achieve some goals of a realtime OS what Linux not is!
Several months ago there had been reporting of continious feed at
3MBit/s with rather powerful machines (Pentium II/III, 350+ MHz).
I for myself had first trouble with a ditto dash board and my
ditto 2G, but after assigning it it's own DMA and (!) IRQ it
works reliable. Doing backup with Arkeia I get an average
throughput of about 12-13MB/min over 30 to 60 minutes. That means
the tape keeps streaming.
My Linux box is based on an older Socket 7 Triton based m/b and
operates an IDT WinChip (Centaur) at 200MHz, but my previous
Pentium/75 worked too.
> ...
Good luck
Martin
--
Martin Jacobs * Windsbach * [EMAIL PROTECTED] und
[EMAIL PROTECTED]
Registered Linux User #87175
