On Sun, Apr 01, 2001 at 08:10:02PM +0200, wojtek@wojtek.from.pl wrote:
> > mt status already reports "blocksize: 0 (0, 0, 0, 0)".  I'm now running
> > buffer with bs of 32k.  Network load is about 450K/s which means the
> > larger block size does not help.  This DDS-2 drive should be about twice
> > this fast if everything was ok.
> 
> DDS-2 should give 500kB/s uncompressed speed. compressed differs frm data
> type

Oh yes, I was thinking of the compressed rate.  I can't find the numbers
anywhere in HP documentation (argh, I _want_ technical information!!).

Anyway, I couldn't fit more than 3.2 GB on a 4 GB tape (uncompressed
capacity), so something was (is?) wrong.

On Sun, Apr 01, 2001 at 08:11:36PM +0200, wojtek@wojtek.from.pl wrote:
> try doing it without "buffer"
> 
> tar cvf - <data to backup>|ssh host "dd bs=32k of=/dev/rst0"

Does dd do double buffering?  If not, the tape would stop streaming if
there was a slight delay in network or on the other machine?  I wanted
to use buffer because it does double buffering and simultaneous read/write
to the buffer.

On Sun, Apr 01, 2001 at 09:55:18PM +0200, Bernd Sieker wrote:
> > what blocks does "buffer" program use?
> > 
> > try setting blocks to 0 (mt setblk 0) and set 32kB output block size in
> > "buffer". i do not use buffer no i don't know what's the options
> > 
> 
> Also try to use the "buffer" program on both computers, not only on
> the one with the tape drive.

I increased the block size in buffer to 32k and things got better.

I'm not sure if using buffer at the other end would help - in this case,
I'm copying a bunch of large (> 100 MB each) .tgz files to tape - reading
them off the disk fast enough is not a problem.  I understand that another
buffer could make a huge difference when archiving lots of small files.

Is it normal that every now and then (every 3-4 minutes or so) the DAT drive
does something odd and stops receiving data for a while?  I'm monitoring
the network traffic with netstat -w 10 and the numbers drop every now and
then.  Maybe I should install my old drive and see if it does the same..
but it started eating my tapes :-I

Thanks to all.

  -jm