Hello,
I believe networker Emc already offer capacity based licence for VTL, we 
have them in use and more refined version of stop gap licence we have ( 
unlimited slot 10 TB increment  X 4) licence is in works.
I do believe in larger environment VTL has play, in small to medium 
environment AFTD may suite you better, especially if Networker Disk 
management becomes more rebost, i.e i would like to see it support staging 
along with retention ( for staged data) for number of days so that tapes 
can be written for offsite without loosing onsite recoverability for 
number of days.
Thanks

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