different classes
VTLs of that size usually really seem constant input at far above of what a few thumpers can handle - maybe this is just too much for current deduplication implementations - otherwise it shouldn't be hard to add a "few" nodes into the VTL that are dedicated for deduplication. I dont know if FalconStor also uses dedicated nodes for compression like the "competitior" system we got at our site.
(of course they didnt use a hw gzip engine... nono... never use anything fancy if you can bill much anyway)
also, I could well imagine that the customers in question dont want to rely on some magic black box but rather have a more easily recoverable state on the tapes, in case the datacenter and VTL blow up.