Replicas of the same file reside on failure-independent machines
- Improves availability and can shorten service time.
- Maps a replicated file name to a particular replica.
- Existence of replicas should be invisible to higher levels.
- Replicas must be distinguished from one another by different lower-level names.
- Replicas of a file denote the same logical entity - an update to any replica must be reflected on all other replicas.
- Reading a nonlocal replica causes it to be cached locally, generating a new nonprimary replica.