Collocation by group - TSM consuming more tapes

nags

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PREDATAR Control23

Hello everyone,

I have gone through few posts here regarding Collocation by group. And its consequences that TSM can consume more tapes when we dont add a node to any collocation group, with the primary tape pool set with -"Collocation-group" parameter, and that the node will by itself seen as a seperate group.

1. I see a lot of nodes in my environment (around 80) which are not added to any colloc group.
2. Besides migration is running all day from my disk and fileclass storage pools to the primary tape pools
3. If i add 5 tapes TSM is picking up all the 5 tapes soon and if i add 15 tapes and its all gone too.
Is this also due to collocation by group and because a lot of nodes hanging in there without being added to any colloc group.
4. I see a lot of filling tapes with anywhere between 1 to 10 percent utilized (LTO 5 tapes) . But TSM keeps picking up scratch tapes from the libr.manager.

Can you please help me in knowing if this tape utilization issue will be fixed once i add all the nodes to the colloc groups defined appropriately.
Or is there something else that i need to look at.

Looking forward for suggsetions.

Thank you.
 
PREDATAR Control23

Like you noticed, if you use collocation by group, and a node is not in a group, then that node is essentially it's own group. So those 80 nodes that are not in a group will each require their own tape(s). That means a minimum of 80 tapes just for these nodes.

You should see a reduction in tape usage once those nodes are added to a group.
 
PREDATAR Control23

Thank you. Will be there be any other consequences by adding the nodes to a colloc group after they have been running backups all this while. I could not think of any. But an expert advice would be nice.
 
PREDATAR Control23

No, that data that has already been backed up will remain on the tapes they are on, until they are reclaimed. Once those tapes qualify for reclamation, when the data is written to new volumes, it will be collocated based on the new settings.
 
PREDATAR Control23

You can do a SQL query and search for volumes with low utilization and copy them out to a file(s) and create move data scripts to consolidate the tapes and regain your scratch volumes. I would also suggest adding a SQL query to check for nodes not in collocation group to your daily monitoring to prevent this from happening in the future.
 
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