Compaq ProLiant 7000 Deploying the ProLiant Cluster for NetWare 4.2 - Page 18

'HSOR\LQJ WKH 3UR/LDQW &OXVWHU IRU 1HW:DUH   ProLiant Cluster for NetWare 4.2 Administration Outlined below are some helpful guidelines to assist you in administering and supporting the ProLiant Cluster for NetWare 4.2. Increasing Availability Intra-cluster Communication Should the servers experience a disruption in intra-cluster communication, they will initiate the failover process. Obviously, this condition is only acceptable in the event of an actual failure that disrupts the server's ability to service client requests. Therefore, the reliability of the connections between the servers in the cluster is a direct measure of the clustered system's ability to maintain costandby operation, wherein both servers are fully operational. There are several ways to reduce the possibility of a disruption of intra-cluster communication. Each method shares an underlying objective: to create redundant paths over which monitoring will continue if the another path is disrupted. The ProLiant Cluster for NetWare 4.2 provides this redundancy through the three lines of communication between servers: the NetWare link, the optional dedicated link, and the disk link. Compaq extends this redundancy with a feature that configures two Compaq Ethernet adapters or two ports on a single adapter, such that one is a hot backup for the other. This feature, called Advanced Network Fault Detection and Correction, is available on all Compaq 10/100 Fast Ethernet products. This feature reduces the possibility of downtime due to network failure by allowing the administrator to configure a redundant interconnect for each communication path. In a redundant interconnect configuration, each communication path is configured with a primary link and a backup link. If a component in the primary link fails, communication continues over the backup link. The redundant interconnect feature significantly enhances the availability of clustered systems. Quorum Arbitration Each server uses quorum arbitration to monitor and verify that the other server is operational. By monitoring the other server's usage of a reserved region on the shared volumes, both servers can be sure that the other is still accessing the storage array. In the event that a server does not update the information in this shared region, the cluster becomes aware of a potential failure. In order to prevent false failovers, NHAS will verify the disk link status 4 times. If after the fourth verification, or roughly 20 seconds, Server B has not accessed the reserved region of the disk, Server A will set the disk link status to disconnected. If the NetWare link (and dedicated link, if implemented) status is also disconnected, NHAS will initiate a failover to Server A. IP and Applications Failover Configuration If you want your IP-based applications to failover to the other server when their host server fails, you must set up your ProLiant Cluster for NetWare 4.2 to redirect all IP traffic from the failed 0096-0699-A