Hi, I cannot answer question directly, but consider these as alternatives:
1) DNS appliance (multi-master), works well and has many nice options: http://www.infoblox.com. This is probably more suitable to running DNS than GSS. BTW, I don't/haven't worked for infoblox. I have deployed them in the past and think they work pretty well.
2) Do you really need GSS appliance in your environment? Before purchasing a GSS, consider this write-up discussing GSLB (first link may not work):
http://www.tenereillo.com/GSLBPageOfShame.htm
http://www.tenereillo.com/GSLBPageOfShameII.htm