The primary purpose of this command is used to see whether NW is capable to use 
the hardware after an installation/configuration. This is it. Or course you 
could also run an ordinary backup and verify/clone the data later. To the best 
of my knowledge, there is no further info (necessary).

If your system is generally working fine i do not expect a general problem 
(with CDI). Instead if you say that this is only during a 're-scan' it looks 
like the media has been stored inadequately and environmental issues may come 
into effect. It could also be a compatibility problem, especially when theses 
tapes might have been used by an earlier standard like LTO3 or LTO2. 

If you need to rescan them you do not even have chance - of course you could 
try a different tape drive but you must retry the scan/recovery until you got 
all your data back.

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