R3: Write Durability — fsync-Before-Ack, Survivor Quorum
Ack only what survived: fsync/group-commit durability barrier, survivor quorum, and read-your-writes — the write-side of the P0 stack.
Ack only what survived: fsync/group-commit durability barrier, survivor quorum, and read-your-writes — the write-side of the P0 stack.