As you didn't specify the platform your libaries are concerned, I'll use
Solaris as an example here ...

o  Install the latest st patch, don't edit the tape-config-list within the
/kernel/drv/st.conf file ...
`
o  Write on a DLT IV type tape in the DLT8000 drive using density 'm' from
the beginning of tape (you may need to force a rewind first) ...
`
o  The Tape will now be in 35GB W/Compression mode and can be read on the
DLT7000 using the 'c' ...


Assuming latest patch and default st.conf ...

               l      m      h      c/u
    DLT 7000  20GB   40GB*  35GB   70GB*
    DLT 8000  35GB   70GB*  40GB   80GB*

               l      m      h      c/u
    DLT 7000  0x82   0x83*  0x84  (0x85)*
    DLT 8000  0x84  (0x85)* 0x88   0x89*

* indicates hardware compression

So from the above DLT7000 /dev/rmt/#cbn = DLT8000 /dev/rmt/#mbn

HTH ... Schlumpf ...

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