NAS / RAID Calculator

Calculate usable capacity, fault tolerance, and cost per TB for any RAID or ZFS configuration.

Usable Capacity — 20TB

2TB500TB

Budget — $2,000

$200$10,000

RAID Level

ZFS — 1 drive failure

Drive Size

ZFS RAIDZ1 Layout

Drives needed

Drive size

20TB

Usable capacity

40TB

Raw capacity

60TB

Overhead

33%

Fault tolerance

1 drive

Estimated cost

$720

Cost per TB

$18/TB

Idle power

~18W

Rebuild risk

~96%

⚠ ~96% statistical chance of an unrecoverable read error during rebuild (simplified model — scrubbing and enterprise drives reduce real risk). Consider RAIDZ2 / RAID 6 for double-parity protection at this array size.

RAID protects against drive failure, not ransomware or accidental deletion. Always maintain offsite backups.

FAQ

What RAID levels are supported?

RAID 1, 5, 6, and ZFS RAIDZ1/RAIDZ2/RAIDZ3. We recommend ZFS RAIDZ1 or RAIDZ2 for new builds.

Does RAID replace backups?

No. RAID protects against drive failure, not accidental deletion, ransomware, or site-level disasters. Always maintain offsite backups.

Which RAID level should I choose?

RAIDZ1 for home NAS with 3-6 drives. RAIDZ2 for larger arrays or critical data. RAID 6 for compatibility with non-ZFS systems.