Nicolaos -

Your session summary numbers show a good "Network data transfer rate"
for gigabit ethernet, but the "Aggregate data transfer rate" number
looks much too low.

The only way to narrow down the problem is to do the analysis there.
Your client may be experiencing file contention: unfortunately, the
Quiet client option is in effect, so you don't have any session
details to inspect.  Perform at least one run without that option in
effect and look for Retry records; and also examine the timestamps
between file Sent records, looking for any unusually long deltas
which indicate slow data acquisition.

If it is not feasible to perform Query SEssion from the TSM server to
watch what this client session is doing, then generate a report from
your TSM server accounting records, which will reveal media wait or
similar issues.  I would suspect that the delays are at the client
end, however, where you may need to perform a client trace to get
solid information, if the accounting records show no TSM server
issues.  It appears that you have aged Windows systems at that site,
which can mean a lot of disk fragmentation.

Also, have a look at "Backup performance" in http://people.bu.edu/rbs/
ADSM.QuickFacts for known foibles which can delay backups.

   Richard Sims