[CentOS] Backup of large filesystems >500GB

I've a small system that I use to support a number of churches. I provide web and email for them. My current server is running CentOS 6.3 with paired 1TB drives in a RAID1 configuration. It works well. One filesystem is very large, >500GB, and contains numerous large files: SQL, docs, church libraries in ebook and digital form, plus stored videos of church services.

My problem is that I've found no means of backing up that file system. Dump and tar both error out as exceeding the maximum size. Neither will backup just the video directory (the largest) even with compression.

Backup will be to an external (USB) removable HD.

Can any suggest a prog or a method to back up this filesystem?

mw