A log-only replica contains only logs and has no MemTable or SSTable.
A log-only replica has the following characteristics:
Contains only logs, has no MemTable or SSTable, and occupies the least memory and disk space.
Participates in log voting, provides external log services, and participates in the restoration of other replicas.
Cannot be elected as the leader to provide database services.
Can join a Paxos group.
Cannot be converted into other types of replicas.
The following table describes more features of a log-only replica.
| Item | Description |
|---|---|
| Replica name and abbreviation | LOGONLY (L) |
| Whether logs are contained | It has logs and participates in voting (SYNC_CLOG). |
| Whether a MemTable is contained | No (WITHOUT_MEMSTORE) |
| Whether an SSTable is contained | No (WITHOUT_SSSTORE) |
| Data security | Low |
| Time to become the leader | Not supported |
| Resource cost | Low |
| Services | Not readable or writable |
| Limits on replica type conversion | It cannot be converted into any other types of replicas. |