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It takes about 20 minutes for a node to come online following start-up. Most of this time (10-15 minutes) is spent updating the packages (like Java and JPackage) from the defaults on the CentOS 5.5 AMI. Therefore the time-to-start could be significantly improved by building a new custom AMI, starting from the base AMI, installing infinit.e-prerequisites-online RPM, and then creating the new AMI (we used that link to generate this script file on github).