I was browsing through twitter mentions of @adrian_otto and found one posted by Ian Thompson mentioning an article about weak randomness in the cloud. It suggests that because there may be insufficient entropy sources on a Cloud Server or instance that it may make it easier to guess random number sequences because different cloud servers [...]

Check my post from today on the Rackspace Cloud blog. It covers several tips on planning ahead when writing a web-scale application.

Imagine that you have a cluster with two machines side by side in an active/standby configuration. Let’s say you have your data replicated, and the systems are basically identical except for the IP address and hostname. You can use heartbeat to share an IP address such that if the primary fails, the secondary takes over. [...]