@ChoYun Lu
Hi,
Clean all does everything that clean does, but all data is zeroed (securely erased) so that it's not recoverable.
clean
Removes any and all partition or volume formatting from the disk with focus. On master boot record (MBR) disks, only the MBR partitioning information and hidden sector information are overwritten. On GUID partition table (GPT) disks, the GPT partitioning information, including the Protective MBR, is overwritten; there is no hidden sector information.
clean all
Specifies that each and every sector on the disk is zeroed, which completely deletes all data contained on the disk.
For your reference:
https://click.linksynergy.com/deeplink?id=kXQk6%2AivFEQ&mid=24542&u1=tomshardware-row-7526672877446980000&murl=https%3A%2F%2Ftechnet.microsoft.com%2Fen-us%2Flibrary%2Fcc766465%2528v%3Dws.10%2529.aspx
Hope above information can help you.
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