Anyway, ZFS gets inline deduplication! This means, that ZFS can decide -on the fly- if a data block was already written by another process at another time and know where that was. It then merely needs to store a pointer to that particular block elsewhere on the disk (an inode) and it's done.
Expensive data center storage solutions such as NetApp and EMC use this technology too, but these boxes cost $100,000+. ZFS is the file system that you use when you format your disks! Any disks! :)