HBase crashed for me this night, due to the extra leap second inserted (2012-06-30 23:59:60).
When attempting to restart HBase, it just didn’t start. I found this resource for a tip that might work to get it up (although I found it after rebooting my servers, so I didn’t try it):
http://pedroalves-bi.blogspot.com/2012/07/java-leap-second-bug-how-to-fix-your.html
All java processes(including all HDFS-related) were using 100% CPU, together with ksoftirq. I turned off ntpd autostart(chkconfig ntpd off), and rebooted the servers, and then started my HBase cluster back up. This solved the issue.
Time. How hard can it be?
http://blog.habets.pp.se/2010/09/gettimeofday-should-never-be-used-to-measure-time