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Tape Compression

Level 4

I have many used tapes with uncompressed format. I believed if the tape media was initialize , there are some header information being written to it. Now I want to use these tapes in compressed format but I was not able to do it. I enabled hardware compression and used a compressed device file, it still detect as uncompressed.

How do I erase the header information in the tapes so that I can use compressed mode ? I tried to re-label the tape using NB GUI but it did not works.

Any suggestion ?


Level 3
I don't know how to setup compression outside of NBU however re-labeling the tape inside of NBU, even if it did work would still write to the tape. And if I had to guess why the label failed would be because the tape was assigned in one of the NBU DB's.

There is also the option to enable compression inside of NBU policies. I would perform a few tests using hardware compression and software compression to see what works best. But be aware that using two forms of compression (both hardware and software at the same time) will almost always be a very bad idea.

Hope that helps

Level 3
Did you change the device pointers in NBU and restart NBU? If you look at the output of tpautoconf -l what does that show you?

Level 3
What OS are you running?

I'd check to make sure compression is enabled at the OS level.

If you are running Solaris for example ensure you have the proper entries in your st.conf file.

Are you confident in the compressibility of your data?

Try using some "zip" application to see who much it compresses.

What is your tape technology?
David A. Chapa
Managing Partner, CTO
Co-Author, Implementing Backup and Recovery