Prof. Eitan Bachmat

Traditionally, there are two main forms of data replication to secondary locations: continuous and snapshotbased. Continuous replication mirrors every I/O to a remote server, which maintains the most up-to-date state, though at a large network bandwidth cost. Snapshot replication periodically transfers modified regions, so it has lower network bandwidth requirements since repeatedly overwritten regions are only transferred once. Snapshot replication, though, comes with larger I/O loads on primary storage since it must read modified regions to transfer. To achieve the benefits of both approaches, we present hybrid replication, which is a novel mix of continuous replication and snapshot-based replication. Hybrid replication selects data regions with high overwrite characteristics to be protected by snapshots, while data regions with fewer overwrites are protected by continuous replication. In experiments with real-world storage traces, hybrid replication reduces network bandwidth up to 40% relative to continuous replication and I/O requirements on primary storage up to 90% relative to snapshot replication.