I'm well aware of SNMP, we're using it now to monitor the appliances globally ; however, I'm wondering if the mcafee appliances themselves have some way to create customized threshold alerts ( warnings).
It would be a nice feature tool to add especially in such cases when a machine is rampant with spyware or generating spyware\ virsuses at high rate, etc. Yes you can always look at the DashBoard to get this info but that's not really a PROACTIVE solution in a large environment.
There are some built-in properties that can monitor the health of the proxy and send alerts (email,syslog,snmp traps)
The default Error handler has rules for some of them. You can look up statistics for CPU , proxy connections, Disk Space, memory usage, network utilization and others to send alerts on. It does not go down to the hardware level, that's where the MIBs would come in for lower-level monitoring.
you might find incident id 20 and 21 useful for RAID and S.M.A.R.T HDD incidents, you can then handle them in the error handler ruleset, and trigger an SNMP trap, syslog, whichever works best for you