In short, raidz is ZFS answer to raid5/6. The basic raidz construct requires 2 or more drives for data and 1 or more (up to 3) drives for parity. The number of parity drives is typically appended to raidz when describing the construct. For example, raidz with one parity drive is raidz1 (often just truncated to raidz), with 2 parity drives, it is raidz2, and with 3 parity drives, it is raidz3.
For optimum performance, it is recommended to use the formula (2^x + p). In this calculation, “p” is number of parity drives, and 2^x is the recommended optimal number of data drives.
Examples: (just examples, using the formula, any variation can exist)
Sub-optimal variations can be used, and ZFS will do its best to make them work.
These vdevs can also be striped.
Some common shapes are:
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