mylvmbackup backup action
It does seem very promising in that it combines both - quick backups like hotcopy and it does table locks only on time required to create lvm snapshot. It seems the only way to backup without long lock.
It is possible and tested by me to use mylvmbackup with backupninja. I've made page in wiki about that:
English: [[backupninja + mylvmbackup]] Russian: [[backupninja + mylvmbackup Russian]]
(from redmine: created on 2011-02-25)