RAID-Z
ZFS's software parity RAID, available as RAID-Z1, Z2 and Z3 for one, two or three parity disks.
RAID-Z avoids the classic RAID 'write hole' and combines with ZFS checksums to detect and repair corruption. Z2 (double parity) is a popular sweet spot for home NAS builds with 6+ drives.
Related articles
ZFS
An advanced filesystem and volume manager offering data integrity, snapshots, compression and software RAID.
RAID(Redundant Array of Independent Disks)
A method of combining multiple drives so they act as one, improving performance and/or protecting against drive failure.
NAS(Network-Attached Storage)
A dedicated storage device connected to your network that lets multiple devices store and access files centrally.