The following list specifies hardware requirements for a Heartbeat cluster. These requirements represent the minimum hardware configuration. Additional hardware might be necessary, depending on how you intend to use your Heartbeat cluster.
A minimum of two Linux servers
The servers do not require identical hardware (memory, disk space, etc.)
At least two communications mediums (Ethernet, etc.) that allows cluster nodes to communicate with each other.
The communications mediums should support a data rate of 100 megabits per second or higher.
A STONITH device