Which of the Following Statements About the Principle of the File

Which of the following statements about the principle of the file system snapshot feature provided by an N8500 clustered NAS system are correct? (Select two)

A) When a snapshot is created, a block mapping pointing to the data on the file system is generated.
B) If an original data block needs to be replaced for the first time, the new data block is copied to the snapshot reservation area.
C) If an original data block is replaced for the first time, the block mapping in the snapshot points to the data block in the snapshot reservation area.
D) If a data block that has replaced an original data block needs to be replaced by a new data block, the new data block is copied to the snapshot reservation area.