High Availability with Open Source

When I build a network or a system, I try my best to make sure that everything is as redundant as possible: redundant power supplies, RAID for the drives in case of a hard drive failure, backup routes in OSPF in case someone trips over the network cable... you get the idea. But what happens if the CPU overheats in one of the web servers and causes it to crash? Or what if someone yanks the network cable from your LDAP server? Or if someone flips the switch and accidentally turns off the accounting database server? If you incorporate High Availability (HA) into your system design, the answer is "nothing". Your web site will still be running, your network users can still login, and the accounting department won't notice any glitch. You don't even have to leave your desk.

Open Source makes HA easy to implement, with offerings like heartbeat, keepalived, and CARP.

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