As far as I know, there still exists no sane backup strategy for multiple filers, unless you think having one tape library per filer or backing up multiple terabytes of data over the network and through some kind of backup management box is sane.
It can be, considering that often it is cheaper to buy the hardware to set up your own dedicated backup LAN than buying the hwardware to set up your own dedicated backup SAN.
But if you have a pre-existing SAN and a Vixel switch, NTAP's new solution seems ideal.
Bruce