An active/backup cluster is a cluster in which one node provides highly available services and the other node serves only as a backup.
In an active/backup configuration, only one node is providing a particular highly available service. The other node is only a backup for that highly available service.
A cluster is a pair of nodes with shared disk storage and connected for IRIS FailSafe use.
A configuration file is a file created by an administrator of a cluster that specifies information about the hardware and software configuration of the IRIS FailSafe system. It is installed in /var/ha/ha.conf on both nodes in a cluster. These files must be identical on the two nodes.
A dual-active cluster is a cluster in which both nodes provide highly available services during normal operation.
In a dual-active configuration, both nodes are providing a particular highly available service during normal operation.
A fixed IP address is an IP address that is not failed over (in other vendors' high availability implementations this is sometimes called a node IP address). Each interface used by IRIS FailSafe must have exactly one fixed IP address. Fixed IP addresses are configured in the file /etc/config/netif.options. Usually, the hostname of a node is an IP name for one of the fixed IP addresses on the node. Typically, IP addresses used for primary interfaces and private interfaces are fixed IP addresses.
Heartbeat messages are messages sent between the nodes that indicates a node is up and running.
A high availability IP address is an IP address that is failed over by IRIS FailSafe (in other vendors' high availability implementations this is sometimes called a service IP address). It is configured by IRIS FailSafe and used by highly available services.
Highly available applications are client/server applications that have been configured to run in an IRIS FailSafe cluster. If the IRIS FailSafe system detects a failure on the node on which a highly available application is running, all highly available applications and resources are shut down on the failed node and restarted on the other node in the cluster.
Highly available resources are the I/O devices (interfaces and disks) that have been configured as highly-available services on the nodes in a cluster.
Highly available services are interfaces, disks, and applications that have been configured to fail over to the other node in a cluster under the direction of IRIS FailSafe software. Highly available services can be divided into two categories, highly available resources and highly available applications.
An interface is a hardware connection on a node to a network. Typical interface names are ec0 and fxp0 for Ethernet networks and xpi0 for FDDI networks.
An IP address is a network address specified as a name (a string) or in internet address notation (X.X.X.X). The use of internet address notation is required in some cases and strongly recommended in other cases because the name lookup time (see the resolver(4) reference page) can be excessive and cause IRIS FailSafe to assume a failure. You can manually configure an IP address to an interface with this command:
# /usr/etc/ifconfig if_name inet ip_address
if_name is the interface name and ip_address is the IP address (name or internet notation). Configuring an IP address to an interface is normally done by the startup script /etc/init.d/network.
An IP alias is an IP address that is an additional network address for an interface. It is also known as a high availability IP address. When there is a failure on a node, IP addresses move from their primary interface to their secondary interface (on the other node). IP aliases are listed in /etc/hosts. Configuring an IP alias to an interface is done by IRIS FailSafe, according to specifications in the IRIS FailSafe configuration file.
An IP name is an IP address in name (string) form. Specifying an IP name for a network address in internet address notation (X.X.X.X) is done in /etc/hosts.
An IRIS FailSafe system is a cluster running IRIS FailSafe software.
A MAC address is a hardware-level Ethernet address. In most situations, MAC addresses are failed over automatically using the IP re-arp protocol. On Ethernet networks, for the few situations where the re-arp protocol isn't supported, IRIS FailSafe provides an alternate mechanism for MAC address failover (this mechanism, called re-mac'ing, isn't available on FDDI networks). See the section “Network Interfaces and IP Addresses” in Chapter 1 for more information.
A node is a CHALLENGE Server.
A private interface is a network interface that is connected to the private network between nodes.
A private network is a network connection between the nodes in a cluster that is not advertised to other networks.
A public network is a network connection between the nodes in a cluster and the clients who use the highly available services provided by the cluster.
Re-mac is a mechanism used to change the physical address of a network interface. The change is not persistent across reboots.
A serial connection is the serial line connection between the nodes in a cluster that provides a mechanism for one node to reboot the other node immediately.