Tape usage - 3592 media 9

[herveymtz]

I've done a search on your forum to see if I could find anything on this and I didn't.

We use tapes as on-site backup storage but have not been able to determine why our volumes are not utilized to their fullest. I've a ticket open with IBM for sometime and we are at a standstill on this issue.

Anyway, these tapes can handle up to 1.2 TB of compressed(3 to 1) data and the most amount of data that we can get on these is around 700 gig.

I guess what I'm asking is can TSM compress data? IBM tells me that yes it does, but we can't seem to get anymore data to stack on these.

If TSM does compress, how come we can't get more data(somewhere close to the 1.2TB) on these tapes?

 

[cwilloug]

What Tape Library are you using? And what kinda of tape drives?

 

[herveymtz]

What Tape Library are you using? And what kinda of tape drives?

It is a 3584 library and the dirves are 3592.

I forgot to mention that TSM is running on the mainframe under z/OS

 

[Eldoraan]

How much of the data is already compressed on the client? TSM can't compress a compressed file any more than it already is - and actually it usually causes the file to expand.

 

[herveymtz]

How much of the data is already compressed on the client? TSM can't compress a compressed file any more than it already is - and actually it usually causes the file to expand.

Our clients are set-up to NOT compress.

 

[Eldoraan]

I'm talking about the data on the client - not client compression. If you're backing up .zip or .gz or any other comressed file, it's not going to be compressed further. We have MS SQL databases that generate compressed dump files via a product called LiteSpeed. Those databases are not compressed further in TSM, so the tapes they get written to show closer to native capacity of tapes.

 

[herveymtz]

How much of the data is already compressed on the client? TSM can't compress a compressed file any more than it already is - and actually it usually causes the file to expand.

None of our clients produce compressed data.

 

[Eldoraan]

OK, Next thing to look at would be the device class settings. What is the FORMAT parameter on the device class set to?

 

[herveymtz]

OK, Next thing to look at would be the device class settings. What is the FORMAT parameter on the device class set to?

Initially, it was blank; then when I started looking into this issue: it was changed to 3592c, then to 3592-2c then to 'drive'.

 

[Eldoraan]

Well DRIVE will use the highest compression level available on drive, so that should give you best media usage. I wonder if when it was blank, it was using the base native uncompressed 3592 format.

 

[moon-buddy]

In all honesty, I would rather have lower compression of my data rather than a higher one. I can live with a tape getting only 700 GB of data rather than getting 1.2 TB and loose it all together because of media failure. And, yes, the higher your compression, the more critical you need to have the media in 'good' shape.

My two cents.

Obviously, this not what you want. You want more data per cartridge. As mentioned, check the FORMAT parameter and set it to DRIVE to get the highest possible compression.