DRM offsite tape reuse when backup multi storagepool to 1 copy pool ?

[hungng89]

Hi everyone

I am doing deployment DRM tape offsite on our backup environment .
I have question about DRM offsite tape reuse . I 've already read ibm redbook , read quite many thread about this task but still have some confusion .

Example:
My storage pool backup retention is 14 days.
My archive pool retention is 365 days.

I created 1 copy pool .

I've created a daily schedule to backup <backup pool > & < archive pool> to <copy pool> at 4:00 AM
After that i check out the vol and bring it to offsite at 8:00AM

The next day the schedule run and use one new scratch tape to backup stgpool.

My question is , when will my first backup tape ( copy pool ) can be reused as scratch tape ?.

From what i 've read the tape can only be reuse when all old data on it is expired . But if i backup my archive pool to the tape so it can't not be expired because archive retention is 365 days.

Have anyone has any advice , any sample and practices of your current environment ?

Thanks for reading .

 

[Raakin]

Data will expire off the old tapes in one of two ways: the data is old and hits the retention limit or the data is moved (via reclamation or similar process) to a different tape.

Either way your tape will also have to wait until the tape reuse delay limit has been reached as well. This reuse delay allows you to roll-back the TSM DB in the event you need some data that just expired, data corruption, etc.

To add the example:
Backup retention is 14 days
Archive retention is 365 days

You determine what your reuse delay is, for this example let's say 14 days

One might initially think your backup tapes would be able to be used at day 28 (14 days + 14 days) and your archive tapes would be able to be used at day 379 (365 days + 14 days) but that would only be the case if ALL your data was expired. So, if no move processes happen, and the data changes little on your target then your tapes will not return to scratch for AT LEAST 28 days and 279 days respectively.

Most likely ALL your data will not expire at the same time and then, without rewriting a redbook, you have your settings (like reclamation) to allow TSM to manage your data or manage your storage (Tivoli Storage Manager).

Your question when can you reuse a tape, the answer is who knows! Well, TSM knows when it can reuse the tape because it manages your data.

You might be able to get a best guess with more information. The settings I can think of off the top of my head, early this morning, that could possibly influence the answer to your question: Retention settings, reuse delay, actual amount of GB on tape, expiration of data delta on backup node, reclamation threshold, how often expiration is ran on TSM server, type of tape (i/o of tape), number of tape drives and actual speed of tape drives.

 

[ChrisRees]

Hi

If I were you I'd have two copypools, one for archive data, one for normal backup data.

Cheers

 

[hungng89]

Hi Raakin and ilove tsm .

Thanks for your clear explanations , i have created two copy pools for them now . I don't want to mess with the guess game lol )

Thanks