Veritas Filesystem and Volume Manager tools are very cool. You can do everything while the system is online. I wouldn't recommend doing work at peak work times, but you could if you had to.
Filemanager is a very good tool although I don't have any experience with it. But if I go based on my other experience with Veritas, it should be an awesome tool.
HPUX has an LVM tool that is a stripped down version of the Veritas volume manager, but they use the VXFS filesystem format.
Hands Down Veritas is the best one that I know. Also, the NetBackup tool they have is in use Enterprise wide by my major telecommunicationscompany employer in all 13 states in which we operate!
