This read-only Unsigned32, in MB, indicates the amount of data unit replaced in the DRE cache over the last one hour, since older data units are evicted in FIFO order as new ones are written when the cache is full. An admin uses this as a churn-rate indicator, showing how much new, unique data has recently displaced older cached content. A high replacement rate here would tell an admin the working set of WAN traffic exceeds what the current DRE cache size can retain for effective deduplication.