[Beowulf] How to set up 2 Node Failover Cluster
Lombard, David N
david.n.lombard at intel.com
Wed Jan 14 10:32:11 EST 2004
From: Michael Damböck; Wednesday, January 14, 2004 3:06 AM
> Hello everybody,
> I'm told to set up a 2 Node Failover Linux Cluster.
> Is ist possible to do this using beowulf? I've been google-ing all day
> but unfortuneately I didn't get what I was looking for.
No, and yes. No, Beowulf doesn't provide failover; yes, you can use failover within a cluster with good and desirable results.
The biggest issue is what the failover will handle, as that determines the software you need.
For example, do you want to provide a highly available NFS server? Web server? Cluster headnode? Other "stateless" server? Database? Queuing system? Something else?
The NFS and web servers, cluster headnode, and other "stateless" servers can be handled by "heartbeat" at http://www.linux-ha.org/download/ This code allows you to define highly available resources that are managed by heartbeat, the failover manager. You'll typically have heartbeat own a well-known highly available IP address along with any other resources, e.g., shared storage. Heartbeat will only allow one of the two nodes to host the HA resources until that node fails, heartbeat will then start the resources on the other (backup) node and optionally disable the replaced server via a STONITH (shoot the other node in the head) mechanism to prevent a "split-brain" situation where two nodes think they own a resource. The limitation to heartbeat is that it cannot manage any shared state, as you would find in a database server or queuing system.
For an HA database or queuing system, you'll need to look at an app that specifically provides that capability, e.g., SGE for queuing. Even in these latter cases, you still may want to use heartbeat to provide a well-known HA IP address to host the HA app.
David N. Lombard
My comments represent my opinions, not those of Intel Corporation.
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