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Provided I only require virtual IP (migrated between servers), is there any sense in using heartbeat, or CARP is enough?

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up vote 4 down vote accepted

CARP will handle moving the IP from box A to box B (and optionally back again), however it won't do anything else -- If you're absolutely sure you don't need to do anything else (like change a DB from slave to master, Start or Stop some service, etc.) CARP should be adequate for your needs.

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Thanks! Just one point to verify - is there any difference in reliability between heartbeat and CARP (which AFAIK has STONITH capabilities)? – SyRenity May 5 '11 at 14:40
"heartbeat" is both a generic term for communication between two nodes to verify that the other node is alive (CARP uses heartbeat in this sense) and software that implements other features like being able to start/stop services (examples include hadaemon). CARP has limited STONITH capabilities in that it can be configured not to move the virtual IP back to the original box after a failure, but it's not a complete high-availability solution: It's only concerned with the virtual IP. – voretaq7 May 5 '11 at 14:47
So if comparing heartbeat (hadaemon) and CARP, is there any sense to invest time into learning heartbeat, or CARP is enough? Also, from what I read, hadaemon can actually kill nodes (hence the STONITH functionality), can CARP do this too? Finally, is there a limit to how many nodes can be protected by hadaemon or CARP? – SyRenity May 5 '11 at 18:41
If we're talking about FreeBSD, you have the option to use devd to execute a script when the carp interface activates / deactivates. Which could do any DB switching or what not. Like suggested in the fbsd handbook. – baloo Mar 23 '12 at 13:03

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