Compaq AAR-88LB-TE manual Quorum Issues, Server-Process Partition States

Architectural Changes

3.8 Quorum Issues

3.8 Quorum Issues

Network partitioning in RTR Version 3 is based on a router and backend count, whereas in RTR Version 2 it was based on quorum. However, quorum is still used in RTR Version 3; state names and some quorum-related displays have changed.

Additionally, the quorum-related condition of a node in a minority network partition is handled more gracefully in RTR Version 3. In RTR Version 2, a shadowed node in a minority network partition would just lose quorum; in RTR Version 3, the MONITOR QUORUM command states that the node is "in minority," providing more information. The algorithms used to determine quorum have also changed significantly to allow a more stable traffic pattern.

3.9 Server-Process Partition States

As in RTR Version 2, there are three server-process partition states:

•Primary

•Standby

•Shadow

With RTR Version 3, a server process that is initially the primary in a standby or shadow environment returns to primary after recovery from a network loss. (With RTR Version 2, there was no way to specify which node would become the primary after network recovery.) Unlike RTR Version 2, where the location of a primary server after a network outage was unpredictable, as long as servers have not been restarted and both servers are accessible, RTR Version 3 retains the original roles.

With RTR Version 3.2, RTR provides commands such as SET PARTITION /PRIMARY that the operator can use to specify a process partition state.

Architectural Changes 3–3