>This makes sense to me, but I have a few questions. According to my
>library docs, enabling Auto Clean "Allows the library to clean the
>tape drives automatically as needed." How does the library know when a
>drive needs cleaning?


>Is this via some SCSI message that corresponds
>to the Drive Clean light on the drive?

yep.

>Also, how will I know when I
>need to put in a new cleaning tape?

aha, that's a flaw in this whole diabolical autoclean plot - the 
library has no way of warning you that your cleaning tape is about to 
run out!
(although as of this writing, this problem also exists if you use 
NetBackup for your drive cleaning... but you can script a 
cleaning-tape-checking solution in that case)

The specifics will depend on the model of library you're using, but 
an error status will be reported on the library LCD when either (a) 
the cleaning tape hits its configured max number of cleanings, and/or 
(b) a cleaning operation fails because the cleaning tape has reached 
its configured max number of cleanings.  So unless you have VERY 
observant and quick-reacting operational staff, you will probably end 
up having some jobs failing from tape errors before you get the tape 
replaced.

But given the anecdotal reports of DLT drives going for months at a 
time without needing a single cleaning, that cleaning tape might last 
a ridiculously long time before it gets used up.

HTH
rob