How does Isilon SnapshotIQ use storage for snapshots?

A.
Through Changed Block Tracking and only changed data blocks are saved

B.
Works on the file level and saves the entire file no matter what has changed

C.
Works with 4 KiB blocks and will always use that amount of storage, no matter what has
changed

D.
Through Changed Block Tracking and always uses a 4 KiB block, even if the data changed is
less than that amount

Explanation: