Spillover is only an act of last resort, and it'll happen only at 100% (ignoring space of course that's set aside for VHS).  You should never let it happen if you can avoid it.  Why?  Because it could cause terribly inconsistent performance, especially if the 2 node pools are vastly different, like NL410 nodes and S210 nodes for instance.  So if you're getting close to full it's time to get a quote for another node in one of those node pools.  ~Chris
I have 2 node pools, with policies putting all directories into 1 of the 2 pools (business requirement) and global spillover enabled. My question is with one of the pools filling up, at what point will the policy be ignored and spillover happen? Will it happen at a specific percentage or only occur when the pool hits 100%, which according to the best practice guide you shouldn't allow a pool to get that full?
Multiple node pools - whendoes spillover occur?