Estimate active flows and flow-cache utilisation from host count, flow rate and average flow duration.
Flow arrivals and flow lifetime multiply to give the live population, exactly as with sessions. Comparing that against the exporter's cache size tells you whether flows age out naturally or get force-exported when the cache fills. An overflowing flow cache fragments long flows into many partial records, inflating collector storage and breaking any analysis that depends on complete flow duration or byte counts.
Flow Count
active flows = new flows per second × average flow duration; new flows/s = hosts × flows per minute ÷ 60.
active flows = new flows per second × average flow duration; new flows/s = hosts × flows per minute ÷ 60. Flow arrivals and flow lifetime multiply to give the live population, exactly as with sessions. Comparing that against the exporter's cache size tells you whether flows age out naturally or get force-exported when the cache fills.
An overflowing flow cache fragments long flows into many partial records, inflating collector storage and breaking any analysis that depends on complete flow duration or byte counts.
This calculator takes 4 inputs: Active hosts, New flows per host per minute, Average flow duration, Flow cache size. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.