In the device properties, you should set the block size accordingly.

Remember, that the tape must not necessarily be the first in a sequence. Try 
another one.

Also, do not forget that you must first create a client which has already been 
deleted to be able to add CFI info.

If you want to get more info about the tape itself, may i suggest you run 
"mminfo -n -mvv \\.\Tape0 > outfile.txt" first. Then thoroughly check the 
output file.
Unfortunately, you need another scan later to add the information.

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