We monitor CPU andmemory utilization with cacti (a related topic for cacti monitoring https://forums.ruckuswireless.com/ruckuswireless/topics/anyone_using_cacti )
In the past with a ZD3kwe’ve set an alarm threshold for the CPU utilization of 60%, relative to theload we had.
It depends on how manyAPs you use and the load (in terms of number of clients). In our case (multipleSSIDs, 2 802.1X SSIDs, DVLAN) the CPU of ZD3k spiked at 90%-100% several times with6k simultaneous clients, 450APs, resulting in ZD unresponsive. These numberswere less than the theoretical limits of 1k APs and 10k clients for ZD3k. Since we changed to a ZD5k, the CPU did not wentabove 15%.
We also did a httphealth check for the ZD web interface (script which sends an alarm if the ZDurl is unresponsive).