Use what Teraku said, Enderchests with a diamond.
The pros and cons between the Safe and the Enderchest are:
Safe can't be destroyed, the Enderchest can however.
The Safe can't share it's inventory between dimensions and other safes, the Enderchest can.
IF the Safe gets deleted/destroyed, you'll probably lose it's contents. The Enderchest inventory will still exist (unless you delete it's datafile) across all dimensions and can be accessed again.