Hi Nancy,
we also worried about this issue, so we did some tests.
We are using 9x3590E drives using Extended Length carts.
As you suggested it would seem to be best to set collocate to no, to
maximize the amount of threads you can start from a tape-pool point of view.
But the downside of this is that all you client's data gets spread out on
all available tapes. This would require a massive amount of
mounts/seeks/rewinds, which will slow the restore down, when measuring the
overall performance. At our shop it did.
Best way is to backup do collocation on either node or filespace. To use the
benefit of the multi-session restore you should make a storage pool backup,
which you should do anyway. The available resources in the copypools will
also be used when performing a multi-session restore.
Another important issue is the load a client can process. Don't try running
a 6 session restore on a single client-CPU or on a client on a 10Mb/s
network. This will also slow things down.
Play around with the resourceutilization (dsm.opt/dsm.sys) and the maxnummp
(node definition on TSM server) settings to find out the best settings per
node.
When the resourceutilization is set to 10 while the maxnummp is set to 5,
only 5 sessions will be used.
Also prevent a single client from claiming ALL drives when restoring. Make
sure other nodes and house-keeping processes can use resources as well.
Hope this is helpfull.
kind regards,
Ilja
-----Oorspronkelijk bericht-----
Van: Nancy R. Brizuela [mailto:Brizuela AT UWYO DOT EDU]
Verzonden: vrijdag 18 april 2003 18:18
Aan: ADSM-L AT VM.MARIST DOT EDU
Onderwerp: Restores--multiple threads vs. collocated
Hello All,
We are considering the pros and cons of using collocation at our site.
Has anyone done any experiments with restoring using collocation (with a
single thread using one tape drive) vs. restoring using multiple
threads, (multiple tape drives, no collocation)? We are using 3590
tapes with a capacity of 40 gb's, so most of our machines would have
their backup data on one or, at most two tapes, if we collocated. So,
if we collocated, we would usually not be able to use multiple threads.
It seems like we might actually have faster restores by not collocating,
therefore have data on multiple tapes, thus be able to restore using
multiple threads. Anyone have any advice, results from experiments,
thoughts on this?
Nancy Brizuela
University of Wyoming
IBM Systems Group
Ivinson Room 238
(307)766-2958
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