You need to be aware of these issues:

  - To the best of my knowledge, this is officially not supported.

  - Using different pools and assigning specific devices to them will work in 
general.
    However, the manpage states that the media can just be MOUNTED in these 
drives. 
    That means that you can in fact label tapes in the wrong device.
    Of course:
       LTO4 media in LTO5 drive will work.
       LTO5 media in LTO4 drive will not work.

Just be careful.

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