A buffer is a capacity decision
Temporarily retaining data when a database or network is unavailable supports continuity. OPC Router offers Store & Forward as an add-on; confirm availability and behaviour for the selected version and connection. Storage is finite. Power loss, disk failure, queue limits or misconfiguration can still affect delivery, so buffering should not be described as an unconditional zero-data-loss guarantee. Decide which outage you need to cover and for how long before choosing storage.
Estimate the raw volume
Raw space is approximately records per second multiplied by bytes per record multiplied by outage seconds. At 100 records/s, 500 bytes/record and a four-hour outage, the raw volume is 720,000,000 bytes, or about 0.67 GiB. Field names, indexes, queue representation and filesystem overhead may increase actual storage. Multiply the raw estimate by a measured overhead factor and a safety margin. The calculator's default factor is an editable planning assumption, not a product specification or capacity guarantee.
Calculate backlog recovery
New data continues to arrive after the connection returns. If the destination can process 150 records/s while the source produces 100 records/s, the old backlog drains at only 50 records/s. A four-hour backlog of 1,440,000 records therefore takes approximately eight hours to clear. If destination throughput is equal to or lower than source throughput, the backlog cannot drain. More disk space alone does not remove this bottleneck; investigate destination writes, batching and source sampling.
Verify behaviour on site
Set alert thresholds for disk use and the age of the oldest queued record. Test ordering, persistence through restarts and duplicate handling at the destination. Reconcile source and destination record counts. Redundancy and Store & Forward address different failure modes; neither automatically replaces the other. Before production, run an outage and recovery experiment using a representative workload. Update the estimate from observed record sizes, throughput and queue behaviour rather than treating the initial calculation as a final hardware design.
Technical references
Check manufacturer documentation for product capabilities. Project steps and examples were prepared by OPC Turkey.