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Storm Control, Unknown Unicast & CAM Ageing Timers

Never thought I'd need this, but traces show clearly unknown unicast flooding.  This flooding tallies up with server interruptions on NFS mounts used for databases.  The outcome is highly undesirable as it interrupts database connections.

I am really apprehensive about using storm control for unicast - anyone have any guidance (seems like treating the symptom not the problem to me, but forgive my ignorance, never used it)  and also, how does one distinguish good unicast (via an existing entry in the CAM table) versus unknown (flooding where it is not known).

In respect of extending CAM aging timeouts too - which is my preferred option - anyone had any recommendation there?  I have read about bringing it in line to ARP timers, which seems sensible as presumably ARP would force the datapath to relearn on the broadcast/ response.  I was effectively going to extend thie beyond the length of time where flooding started to when it flooding stopped, which must be in excess of 5 minutes (so increased there as appropriate - will check traces for this value).  I am apprehensive again of extending this value arbitrarily and without some substance in justifying what the new value should be and why I ahve chosen it.

Bit concerned this is happening as i have a vss configuration connected to a vPC configuration.  I was under the impression control data is synchronized across both, so I am quite confused even if the switch path was asymmetric I was expecting the CAM table entries be passed onto each pair of vPC/VSS (in a square formation, physically)

Any one care to comment - welcome any feedback, many thanks.

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