i have a new TL2000 with a LTO4 tape drive and run BE 2012 on w2k8. I have set BE 2012 to use hardware compression if available or software. My backups don't seem to be compressed. I went to the web gui of the TL2000 and went to Monitor Library-->Drive Identity and Data Compression is set to no. So is Data Compression being used or not?
You have everything set correctly for compression to work. What you will need to do is to check in backup exec and see what it list the compression on the media is. As by looking at the drive identity page is not always current unless there is a tape in the drive. Also if the files that you are backing up have been compressed by there software, or application & the drives sense that it has been compressed once then the drive will not compress the data a second time.
Please let us know if you have any other questions.