You can setup your DFM server (or HPOV or whatever else you might have) to accept snmp traps from your filers. Then setup DFM to fire off a mail or some pager mail. The lag you are seeing is often because it tries a few times to reach the filer before it declares it dead (or some DFM bugs...). You may also have lags in your mail system that won't be helped even if you send your traps to the DFM server. All of this is documented in the DFM documentation.