Tapepool-tapepool usage

[zRich]

I'm a newbie to TSM and trying to figure out what my predecessor did. I’ve been looking at the admin guide but can’t find the info, or don’t understand how the diskpool to tapepool scenario works. I'm scheduled for training but need to figure this out asap b-cuz we're running out of space.

Background info:
We have a tape robot w/ 30 DLT-40/80GB tapes for a 1200/2400GB tape pool. I have a 12 disk-disk pool of 240GB total (20 GB ea.).

When I query the volume, I see that all but two of my tapes are full. Those two are filling, but the percent utilized for about 6 of the others is only 34%-50% and they report that they are full.

Then the 12 disk pools all report that they are only 12-22% utilized.

Two questions:

-How do I get more utilization from the tapes that report low utilization?
-How do I get more data to stay on the disk pools?

Thanks!

 

[comtec17]

-How do I get more utilization from the tapes that report low utilization? - This will depend on what is on the tape. If this is an archive backup, it will not expire until the data on the tape expires.

-How do I get more data to stay on the disk pools? - Disk pools are meant for staging data and should not be used to store data for long periods of time without backing up the diskpool to tape.

 

[Yrrk]

Generally speaking as data expires, holes appear on your media. Thats why over time your percentage utilized will slowly drop on media as the TSM database expires old copies of the data.

Think of it this way.. When the tape is first written too and filled up, it's not unusual to be 90-100% utilized once it gets to status full. Now as weeks go by, depending on your policies the old copies you backed up typically start to expire. TSM expires the files by marking them expired internally in it's database. However the data is still on the tapes because no process has yet reclaimed that space. This is where reclamation comes in.

It sounds a bit like either you don't have reclamation configured or your reclamation threshold is set so low that TSM hasn't yet reclaimed those tapes. I say this because anything less then 50% utilized is a waste.

Lets say you set up reclamation and set the threshold to 50%. Once a tape drops to 50% utilized, TSM will load a new blank tape and copy all the data still viable from the old tape to the new tape. You now have a "filling" tape that is 50% full. It then marks the old tape aa "scratch", returning it to the pool of tapes available for new data. Thus the space has been reclaimed. Look it up in your administrators manual and figure out whether your environment has it configured.

Theres a balance to be had in setting your threshold since the more aggressive you set reclamation, the more wear and tear you put on the tapes and drives. Also it's somewhat dependent on how aggressively you expire old data.

disk pools usually either have high utilization if caching is turned on, or low utilizaiton if not. The idea here is TSM should be pushing the data from disk to tape during off hours or when it needs more space in the disk pool. This process is called migration. I wouldn't worry much about the utilization of your disk pools as the data is not meant to stay there for long.