If VTS is artifically configured TSM server backend this leads to another
question - virtual volumes performance.
We read recently on the list that TSM using VTS is having not so good
performance. Is this true or not I cannot prove and cannot have clear
opinion.
But virtual volumes are by definition TSM server backing up to TSM server.
And if TSM-TSM performance is good why not TSM-VTS (i.e. TSM) performance
be good? And how we can define "good" or "better" or "average"? If TSM-VTS
is performing "not so good" is TSM-TSM having similar performance (measured
in GB/hour or something similar)? If both perform at comparable speeds can
we say both are "not so good" or TSM-TSM performs better?
Sorry for asking so many questions. I have no mainframe (and VTS) to answer
them by myself.

Zlatko Krastev
IT Consultant





Michael Bartl <michael.bartl AT CW DOT COM> on 03.12.2001 10:48:11
Please respond to michael.bartl AT de.cw DOT com
To:     ADSM-L AT VM.MARIST DOT EDU
cc:

Subject:        Re: TSM and VTS

I remember from an IBM presentation a few years ago that the technology
behind VTS is TSM. So using a VTS library on a TSM server means stacking
the same intelligent tape management technology for two instances. This
can eliminate some of the benefits.
On one hand, when collocation is "inactivated" by VTS, access
performance to your data may drop. On the other hand, VTS uses quite a
lot of disk caching to improve performance. It depends on the structure
of a TSM servers data, whether the gain or loss in performance will be
stronger.

Best regards,
Michael
--
Michael Bartl                               mailto:michael.bartl AT cw DOT com
Michael Bartl                               mailto:michael.bartl AT cw DOT com
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Bill Mansfield wrote:
>
> The fact is that TSM does not always write tapes 'til they are full.  If
> you have a bunch of small nodes using collocation or backupsets, you can
> wind up with a lot of expensive tape with little content.  Using the VTS
> would allow you to stack these nearly empty tapes onto one tape.  I'm not
> sure whether this defeats the purpose of collocation, since I'm not sure
> that the virtual tapes will stay collocated inside the VTS, though.
>
> _____________________________
> William Mansfield
> Senior Consultant
> Solution Technology, Inc
>