On Friday, Apr 30, 2004, at 05:33 Australia/Sydney, Ted Byrne wrote:

AIX client v. 5.1.5.5
AIX server v. 5.1.8.0
AIX version 5.2.0.0

We  have a customer who is experiencing discrepancies in performance
between large-file cold backups of Oracle data and LV image backups,
both
sent over the SAN to LTO-2 tape drives.  On the lv image backups, they
are
getting about 70 MB/s sustained.  For the B/A client backups, they are
getting less than 30 MB/s.

<snip>

I have a PMR open with IBM regarding this issue.  Is anyone aware of a
way
to control the block size used for reads by the TSM client?

To the best of my knowledge, you can't. AIX Filesystem I/Os, where
DIRECTIO is not involved, go through the AIX VM subsystem - and may
get split, joined and otherwise mangled on the way through. Some
of this is tuneable through /usr/samples/kernel/vmtune, although
much there is black magic.

I'm assuming DIRECTIO is not involved (as an AIX mount option)?

Just a hunch, but what do your filesystem parameters look like on the
client ("lsfs -q /blah")?

Cheers,
--
Paul Ripke
Unix/OpenVMS/TSM/DBA
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