A resource is the basic unit of high-availability. It is a service or facility which is made to be highly-available by the high-availability cluster[1] resource manager.
A resource is an abstraction which can be one of many different types. It can be something very concrete like a disk volume, or a badge reader, or it can be more abstract like an IP address, or a set of firewall rules, or a software service like a web server, or a database server.
The basic operations which resources have to support include:
start: initiate or gain control of the resource.
stop: terminate or give up control of the resource
status: determine if the resource is started, or stopped.
monitor: determine in more depth if the resource is operating correctly
(Note that R1-style resources[2] must support status, and R2-style resources[3] must support the monitor operation).
The high-availability cluster resource manager tries to make sure that every resource is made available to users by making sure it is running somewhere in the cluster.
The Heartbeat[4] R1 cluster manager, (and many other cluster resource managers) group resources together into groups, called ResourceGroup[5]s. In this case, each group is then started, stopped or moved as a whole by the cluster resource manager.
ResourceAgent[6], primary node[7], hb_standby[8], hb_takeover[9], haresources[10]
| [1] | http://en.wikipedia.org/wiki/Computer_cluster |
| [2] | http://www.linux-ha.org/HeartbeatResourceAgent |
| [3] | http://www.linux-ha.org/OCFResourceAgent |
| [4] | http://www.linux-ha.org/HeartbeatProgram |
| [5] | http://www.linux-ha.org/ResourceGroup |
| [6] | http://www.linux-ha.org/ResourceAgent |
| [7] | http://www.linux-ha.org/PrimaryNode |
| [8] | http://www.linux-ha.org/hb_standby |
| [9] | http://www.linux-ha.org/hb_takeover |
| [10] | http://www.linux-ha.org/haresources |
This information provided courtesy of the Linux-HA project at http://linux-ha.org/