Building Reliable Data Replication at the Edge
We originally built ReductStore to store data on edge devices and read it back by time interval. But a device only has so much disk space. With cameras and sensors writing all the time, we used a FIFO quota to remove the oldest records and make room for new ones. That left us with another problem: how to get the data off the device before it was deleted.
At first, transferring data from an edge device to central storage was a manual job. We used the CLI client or scripts and copied data when somebody remembered to do it. It was always problematic because data collection never stopped. Sometimes we had only two or three days to copy it before it was gone, and a temporary network problem or a missed run could make that window disappear completely.
Automatic replication was the next logical step. The edge is producing a stream of new data, while the central store has more capacity and can have different criteria for what it keeps. We needed to forward new records and configure source-side filters for each destination. Keeping two identical replicas was not the goal.
We also had to keep in mind that the source is usually on the edge. Very often it has no public IP address, and its network connection can be unstable, slow, or absent for long periods. Replication therefore could not make local ingestion wait for the central store. The device still needed to accept data first and deliver it later when a connection became available.



