The following list identifies the system requirements for an HA Branch Server configuration:
NOTE:This will vary depending on the size of the images you distribute to your Point of Service terminals.
The Linux heartbeat software package is used to monitor nodes in a cluster. It exchanges “heartbeats” on the network interfaces of the cluster members to find out which nodes in the cluster are active. If a node fails, it stops emiting a signal. In this case, heartbeat ensures that another node takes over the relevant tasks and identity and makes the failover known within the network. This means that the cluster remains consistent. At present, the heartbeat failover function is limited to two nodes.
Distributed replicated block device (drbd) mirrors partitions and logical volumes (data areas) by means of a normal TCP/IP network. Each node has a particular drbd resource active and all changes are mirrored over the network as secure transactions.
In comparison with RAID1, drbd has additional features for local disks that enable the resynchronization time to be minimized after the two nodes have been disconnected briefly. It also performs a robust check after various malfunctions to establish which side has the latest, consistent data.
NOTE:The Branch Server uses a network block device to replicate the data to the standby node; therefore, no shared storage device is needed.
Figure 7-1 Recommended network card configuration for HA Branch Servers
node1: eth0 151.158.181.28 node2: eth0 151.155.181.29
node1: eth1 192.168.1.1 node2: eth1 192.168.1.2 virtual IP eth1:0 192.168.1.3
node1: eth2 192.168.2.1 node2: eth2 192.168.2.2
node1: eth3 192.168.3.1 node2: eth3 192.168.3.2
WARNING:Because Branch Servers contain sensitive information, they should be secured. We recommend that you close unused ports and allow only the root user to have access to the server console.