Thanks Paul. When I collocated by node I never saw any shared, so perhaps we
either had sufficient tapes or those rules didn't apply to collocation by
node. It would make sense if there were no empty tapes available there would
be some way of satisfying the backup/migration requirement.

Larry Clark
(518) 712-5138 Home Office


----- Original Message -----
From: "Paul Zarnowski" <psz1 AT CORNELL DOT EDU>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Saturday, March 14, 2009 11:41 PM
Subject: Re: [ADSM-L] volumes in a collocation group?

Larry,
This would only be true if you had sufficient tapes so that each
collocation group always has a tape in empty or filling status.
Otherwise,
TSM will start doubling up and putting more than one collocation group on
a
tape volume.

When TSM is writing data to a collocated storage pool, it selects an
output
tape using an algorithm something like this:

1. Select tape in filling status that already has data from that
collocation group on it (or node, or filespace, depending on what level of
collocation you have).
2. If no tapes in filling status exist with data from that colloc group,
select an empty or scratch tape.
3. If no empty or scratch tapes, select the filling tape with lowest
utilization (note that this tape will already be used by other colloc
group
or groups).

If you want to ensure that each tape has data from only 1 colloc group on
it, then you must ensure that you have enough empty/filling tapes to cover
all of your colloc groups.  This is true over time, as tapes fill up.  We
monitor this, to help ensure this.

..Paul


At 11:23 PM 3/14/2009, Larry Clark wrote:

What you say is curious..............only nodes that are in a collocation
group should have data on the volumes in that collocation group. At least
that is my understanding.

Your saying more than one collocation group can store data on the same
volume?

I know for collocation by node that would not be true............

Larry Clark



----- Original Message -----
From: "Nick Laflamme" <dplaflamme AT GMAIL DOT COM>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Saturday, March 14, 2009 8:41 PM
Subject: Re: [ADSM-L] volumes in a collocation group?

On Mar 14, 2009, at 5:13 PM, Larry Clark wrote:

Hi,
Would someone have a query that returns all the volumes in a
particular
collocation group (within a copypool)?

QUERY NODEDATA COLLOCG=grpname STG=stgname

I suspect your mental model of how collocation works is a bit tangled,
because other collocation groups can have data on the volumes returned
by the query, but this is probably what you want.

--
Paul Zarnowski                            Ph: 607-255-4757
Manager, Storage Services                 Fx: 607-255-8521
719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu