Scrubbing corrects on disk bit flips. An in-memory bit flip (which is more rare than on disk bit flips even with non-ECC memory) can corrupt a in-memory data st

Scrubbing corrects on disk bit flips. An in-memory bit flip (which is more rare than on disk bit flips even with non-ECC memory) can corrupt a in-memory data structure which is later written to disk to all replicas, i.e. scrub will not detect it. If this corrupted data structure is later loaded and used this may cause all kinds of problems and there is no tooling to correct it.