Good documentation on hearbeat

[Stephen]

Anyone have any really good documentation on heartbeat, and how it
works at hand, stuff they found particularly good reading?

I might need to build a storage cluster and we are thinking of using
OpenFiler which uses heartbeat for clustering.

if you have anything i should keep an eye out for or a specific read i
would be grateful.

-- 
A mouse trap, placed on top of your alarm clock, will prevent you from
rolling over and going back to sleep after you hit the snooze button.

Stephen