After some sprint coding and testing I am more than happy to declare Xtrabackup getting into alpha stage. And alpha means more that we have some dirty hacks in code / not fully scripted builds / not fully tested all MySQL versions, but backups work just fine! I am able to backup our production box and restore it!
As there were some questions how xtrabackup works, let me explain it: it is supposed to be online, non-blocking backup solution for InnoDB / XtraDB engines for MySQL 5.0 / 5.1 versions. Currently we tested only for 5.0.75 / 5.0.77 and it works just fine. We also modified innobackup script ( thanks InnoDB for making it GPL), so it can be used to backup of MyISAM tables also.
Beside standard –backup and –prepare options we have implemented –throttle to limit IO activity during backup, so we do not hurt production box by intensive file copying operations.
As for now it is available only in source code version on Launchpad lp:~percona-dev/percona-xtrabackup/alpha-0.2 , after some polishing and more testing we will prepare binary builds. Test it if you can and send us feedback. Enjoy!