1 · Choose a RAID level
NetApp triple parity (triple erasure coding) on WAFL.
2 · Configure drives
3 · Drive class
3.5" nearline SAS/SATA capacity HDD — indicative figures.
Advanced — read/write mix, URE rate
Calculated for planning. We don't publish prices — a 24-year UK reseller, Servnet confirms the exact drives, array and pricing on quote. IOPS, throughput & rebuild are indicative estimates.
What RAID-TEC is
RAID-TEC is NetApp’s triple-parity scheme (triple erasure coding): usable capacity is (n−3) × drive size and it survives any three drive failures. It is intended for large RAID groups of high-capacity drives, where long rebuild windows make a third parity worthwhile.
Like RAID-DP it runs on WAFL, so its write behaviour avoids the classic read-modify-write penalty. Triple parity lets you build wider RAID groups safely — keeping more capacity usable per group while retaining redundancy even mid-rebuild on drives that take a long time to reconstruct.
Fourteen 16 TB drives in RAID-TEC give 176 TB usable and tolerate any three failures — letting NetApp build wide, capacity-efficient groups on large drives while staying protected even during the long rebuilds those drives require.
Advantages
- Survives any three drive failures
- Enables wider, more efficient RAID groups on large drives
- WAFL writes avoid the classic parity penalty
- Two parities still protect data during a single-drive rebuild
Trade-offs
- Three drives of capacity to parity
- Vendor-specific (NetApp)
- Only worthwhile on large drives / wide groups
- Overkill for small groups
Best for
- NetApp groups of large-capacity nearline drives
- Wide RAID groups where rebuild windows are long
- Maximum resilience on high-density NetApp shelves
Consider another level when
- Small RAID groups (RAID-DP is enough)
- Non-NetApp arrays (use RAID 6/60)
- Latency-critical workloads
RAID-TEC — common questions
How is RAID-TEC usable capacity calculated?
Usable capacity is (number of drives − 3) × drive size, because three drives hold triple parity. Fourteen 16 TB drives give (14−3) × 16 = 176 TB usable.
When should I use RAID-TEC over RAID-DP?
On large RAID groups of high-capacity drives where a rebuild takes a long time. The third parity means two are still in reserve while one drive rebuilds, so a multi-failure event during the long window is survivable — and you can build wider groups safely.
Is RAID-TEC the same as RAIDZ3?
They are both triple-parity (survive three failures, (n−3) usable), but RAID-TEC is NetApp WAFL and RAIDZ3 is ZFS. The capacity maths is the same; the implementation, performance behaviour and overheads differ.