Hi John,
I should have included more caveats in that message; I didn't mean to imply
that AIX performance is ALWAYS better than OS/390. You can certainly set up
configurations where either OS/390 performs better, or where AIX performs
better. And I am certainly not an AIX wizard, my background is primarily in
OS/390 performance & storage management.
In many cases, as you said, people get better performance on TSM/AIX simply
because they are running the AIX TSM server on a dedicated host and don't
have to fight for resources.
The AIX TCP/IP stack also performs much better than the TCP/IP stack on the
earlier versions of OS/390; in every release of OS/390 that is getting
better.
And it appears to me that AIX has a shorter code path for doing I/O than
OS/390. AIX also uses all the available free memory in the box for (in
OS/390 terms) I/O buffers, and the I/O just flies, even though the AIX boxes
don't have the back end I/O processor hardware that mainframes do.
On the other hand, many OS/390 systems benefit from having a lot of I/O
paths available where you can tune and spread the I/O around, where some
people order AIX boxes with just one disk I/O bus (that's a MISTAKE!), so
that you eventually will hit a dead end on throughput.
Now those are all just BLAZING GENERALITIES, I know -- and I'm the first to
tell you that the answer to all tuning and configuration questions is: IT
DEPENDS!!!
My intent was just to assure the original writer that she could move TSM off
her OS/390 system to AIX without worrying about giving up performance.
-----Original Message-----
From: John Naylor [mailto:john.naylor AT SCOTTISH-SOUTHERN.CO DOT UK]
Sent: Friday, February 21, 2003 4:04 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: AIX TSM better than OS390 TSM ?
Wanda,
You wrote :-
<If you want to save mainframe disk and tape, your best bet would be to
<move
<to TSM on an AIX server (depending on the size of your clients, a WIn2K
<server might do). You get the same great product, terrific performance
<(as
<an ex-mainframer I can tell you the performance on AIX is incredible -
<wouldn't have believed it if I hadn't seen it myself), and NO <conversion
<costs for your clients. You won't have to change ANYTHING on the <client
end!
So why is the performance on AIX so good, compared to the mainframe.
Does TSM inherently run better on AIX, or is it because in many cases
the AIX box will be dedicated to TSM, while OS390 TSM will usually be
sharing
with many other applications, and that it often does not get the resources
it
needs to run at optimum.
We have both TSM's at our site and my perception of the usual applies here
the
AIX TSMs are dedicated, while I have to share a busy mainframe.
John
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