Is the usable size of a RAIDZ array similar to the usable size of a RAID5 array?
The RAID5 calculation is "(N-1) * S", where S is the size of smallest drive. Since most people use the same sized disk in a RAID5 array, this comes out to be "N-1" for most purposes.
Is RAIDZ also "(N-1) * Smin" ?
Similarly, RAID6 is (N-2) * S. Is the usable size of RAIDZ2 similar to RAID6?
for RAIDZ(1) use the same formula as for RAID5. for RAIDZ2 - the same as for RAID6
To complement the accepted answer, a calculator:
Raid Calculator | Raid Disk Space Utilization Calculator | ServeTheHome
RAID5 uses one disk for Parity and requires at least three drives to be used.
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RAID-Z uses one disk for Parity much like RAID5 and requires at least three drives to be used.
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RAID-Z2 uses two disks for Parity and requires at least four drives to be used.
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RAID-Z3 uses three disks for Parity and requires at least five drives to be used.
… and so on.
