Lars Bebensee wrote:

Hi guys,

this is actually not a TSM question but one for the hardware gurus. We are
running a backup under AIX using the savevg command and Ultrium 3580 tape
drives. With topas I can see a data transfer rate of about 1MB/sec. We
attached the drives via Fibre Channel and a SAN Data Gateway. The blocksize
of the drive was set to 2048 (since one of the SAN guys told me FC
transfers with a blocksize of 2048). I started savevg with "-b4" meaning to
write 4x512Byte blocks (=2048). With the mentioned speed the drives are
seriously crawling. Am I missing out something here? Any clues??

Thanks

Lars

Hi,

I think your problem is you are not feeding the data to the tape drive
fast enough for it to stream, therefore it is stopping waiting for data
and then starts when it gets some.  The stop and starts kill the
performance.  I would try increasing two different values:

chdev -l sys0 -a maxbuf=100
savevg -b200 .............

This should improve the streaming of data to the tape drive.  You may
have to play with these numbers some to get the optimal performance.
Good Luck and let us know how you did.

--
Regards,
Mark D. Rodriguez
President MDR Consulting, Inc.

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