Jean-David Beyer wrote:
>
> For this line, the ...rate_limit is 2000 by default. While the tape drive and
> controller are capable of that, my P166 is not reliably capable of keeping up,
> so I slowed it down to 1000 (! Mb) and it works fine. I suggest you try that
> speed first. With a P90, you just might have to go to 500, but I would not try
> it unless 1000 does not work. Mine may restart a block once per entire pass of
> the tape.
>
Actually, now that I think about it, the native "speed" of this drive is
around 10 M/min. It claimed "Up to 20 M/min" in advertising. I used to
wonder why it would 'write' faster than it would 'read'. Verifies
always reported speeds around 9.xx M/min. Once while watching a backup
I noticed that the software would start reporting higher backup rates as
data compression rates went up. I concluded that the inherent speed of
the device was around the 10 M/min. Anything above that was actually the
software reporting speeds based on data compression transfer rates.
This may account for the 'discrepency'. Yes, compression can make the
data transfer faster, but the drive can only write the compressed data
at 10 M/min. Could be a matter of whether you are measuring speed at
the front end, data being transferred, or at the back end, where data is
written. I would guess the numbers you are showing above would be based
on hardware capability and has nothing at all to do with what else your
system is doing. The hardware may never have been capable of any higher
transfer rates (ie the 2000/1000 settings). My p90 can keep up under
windoze (based on advertized claims), so I don't think it has anything
to do with processor speed.
I have a feeling that backing up the same material using both operating
systems would probably bear this out. Not sure it is worth my trouble
however. :)
--
Ken Lowther
Youngstown, Ohio
http://www.atmsite.org
ATM FAQ and more
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