Mirror
Stores duplicate copies across drive pairs. Capacity is roughly half the raw total when using equal-size pairs.
RAW CAPACITY IS NOT USABLE CAPACITY
How much storage will your NAS really give you?
Enter equal-size drives, choose a simple redundancy layout and leave some free-space headroom.
Capacity only. This simplifies common equal-size-drive layouts. Real NAS filesystems, metadata, vendor implementations and decimal/binary unit reporting can change what the operating system shows.
Your drives
What the layouts mean
Single parity
Uses the equivalent of one drive for parity across the set. It requires at least three drives.
Dual parity
Uses the equivalent of two drives for parity and requires at least four drives.
Redundancy is not backup. A second disk copy in the same server does not protect you from accidental deletion, malware, theft or every hardware failure. Read why RAID is not a backup.