zfs-raid-types.md

What is RAID?

RAID (Redundant array of inexpensive/independent disks) is a data storage virtualization technology that combines multiple physical data storage components into one or more logical units for the purposes of data redundancy, performance improvement, or both.

Standard RAID levels

RAID levels and their associated data formats are standardized by the Storage Networking Industry Association (SNIA) in the Common RAID Disk Drive Format (DDF) standard. Please read Wiki page Standard RAID levels, and to get more details.

ZFS RAID types

ZFS user number in the name of RAID (like RAIDZ1) and it may confuse. Number in ZFS RAID means RAID parity, not RAID level. RAIDZ is not exactly the same but very similar equivalent of Standard RAID with benefits of ZFS. For file storages with more than 12 disks ZFS developers propose to use dRAID.

Comparison table

Standard RAID level	ZFS RAID type	Description	Available Storage
RAID 0	Striped ZFS Pool	Data stripe	~97%
RAID 1	Mirrored ZFS Pool	Data mirror	~50%
RAID 5	RAIDZ1	Data stripe with single distributed parity	~64%
RAID 6	RAIDZ2	Data stripe with double distributed parity	~47%
RAID 7	RAIDZ3	Data stripe with triple distributed parity	~38%
RAID 10 (1+0)	Stripe of Mirrored ZFS Pools	Data stripe with series of mirrored drives	~49%

Examples

Striped ZFS Pool (RAID 0)

$ zpool status -v tank-stripe
pool: tank-stripe
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
        /dev/sda1  	ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0

errors: No known data errors

Mirrored ZFS Pool (RAID 1)

$ zpool status -v tank-mirror
pool: tank-mirror
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
      mirror-0      ONLINE       0     0     0
        /dev/sda1   ONLINE       0     0     0
      mirror-1      ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0

errors: No known data errors

RAIDZ1 (RAID 5)

$ zpool status -v tank-raidz1
pool: tank-raidz1
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
      raidz1-0      ONLINE       0     0     0
        /dev/sda1   ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0
        /dev/sdc1   ONLINE       0     0     0

errors: No known data errors

RAIDZ2 (RAID 6)

$ zpool status -v tank-raidz2
pool: tank-raidz2
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
      raidz2-0      ONLINE       0     0     0
        /dev/sda1   ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0
        /dev/sdc1   ONLINE       0     0     0
        /dev/sdd1   ONLINE       0     0     0

errors: No known data errors

RAIDZ3 (RAID 7)

$ zpool status -v tank-raidz3
pool: tank-raidz3
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
      raidz3-0      ONLINE       0     0     0
        /dev/sda1   ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0
        /dev/sdc1   ONLINE       0     0     0
        /dev/sdd1   ONLINE       0     0     0
        /dev/sde1   ONLINE       0     0     0

errors: No known data errors

Mirror of Striped ZFS Pool (RAID 10/1+0)

The array can sustain multiple drive losses so long as no mirror loses all its drives.

$ zpool status -v tank-ten
pool: tank-ten
state: ONLINE
config:
    NAME            STATE     READ WRITE CKSUM
    tank            ONLINE       0     0     0
      mirror-0      ONLINE       0     0     0
        /dev/sda1   ONLINE       0     0     0
        /dev/sdb1   ONLINE       0     0     0
      mirror-1      ONLINE       0     0     0
        /dev/sdc1   ONLINE       0     0     0
        /dev/sdd1   ONLINE       0     0     0

errors: No known data errors