CrashPlan caches resolutions between hostnames and IP addresses. Recently I ran into an issue where a CrashPlan server was moved and we needed to decrease that cache time. In /Library/LaunchDaemons/com.crashplan.engine.plist I found the Java attribute for sun.net.inetaddr.ttl. The default setting for this is 300 seconds. It can be reduced by altering the Dnetworkaddress.cache.ttl string in the ProgramArguments array.
To alter the setting, open /Library/LaunchDaemons/com.crashplan.engine.plist in a standard text editor. Once opened, find Dnetworkaddress.cache.ttl and reduce the ttl value. Once complete, unload/reload:
launchctl unload com.crashplan.engine
launchctl load com.crashplan.engine