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| ShaoLin HA Cluster 1.0 Installation Manual and Operations Guide | ||
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| Prev | Chapter 2. Cluster Hardware Configurations and Installation | Next |
It is important to use the same network adapter for the clusters. The position on the bus slots should be the same for both clusters. For example, the eth0 Ethernet device on cluster A is inserted into PCI bus0. At the same time, cluster B should also have its Ethernet device inserted into PCI bus0 respectively. This will make sure the name space of your network devices identical across the clusters. This is important because during a cluster fail over, Linux OS relies on the network device name space to assign your Ethernet device with the correct network address.
ShaoLin HA Cluster requires the corresponding Ethernet devices of the clusters to connect to the same Ethernet switch or hub to enable IP address failover during a system failover, and heartbeat communications between the clusters. Since Ethernet devices can be used for heartbeat communication and cheap to setup, it is recommend to setup a dedicated Ethernet heartbeat channel for the clusters together with a low-cost RJ45 crossover cable. This will improve the reliability and redundancy of the heartbeat communications. See Section 2.3.1 for more information on heartbeat configurations.
Some system may have not enough number of serial ports for the extra heartbeat communication channel. Since ShaoLin HA Cluster requires at least two heartbeat channels to operate, it is highly recommended to install an extra point-to-point network for heartbeat communications using low cost crossover cables.
When connecting clusters to network, make sure the corresponding Ethernet device is connected to the same Ethernet switch or hub. Otherwise failover will be incorrect and heartbeat communications will fail.
If your system has a serial port, you should use the extra serial port as a redundant heartbeat communication channel. Connect the serial port of the system with a null modem cable. Make sure you connect to the correct corresponding serial port. If cluster A uses /dev/ttyS0 and cluster B must also use /dev/ttyS0. Connecting the cable to an incorrect serial port will cause heartbeat to fail.
If you are going to have redundant heartbeat channels or more than two heartbeat channels, make sure you configure the network interface that is used to serve applications to a CRITICAL CHANNEL. When a failure or timeout of a CRITICAL CHANNEL occurs, the cluster will issues a failover.
ShaoLin HA Cluster allow to use standard RS-232 serial ports for heartbeat communications with an additional low cost null modem cable. It is important to connect the null modem cable to the corresponding serial port of the clusters (e.g. /dev/ttyS0 and /dev/ttyS1). It is highly recommend to use a serial port communication because it can improve system reliability with a minimal cost. See Section 2.3.1 for more information on heartbeat configurations.
