How long does it take to rebuild an 8TB drive in a NAS?
As a theoretical floor, an 8TB drive read or written flat-out at 180–280 MB/s sustained takes roughly 8–12 hours. Real rebuilds run longer — parity computation, concurrent use and throttling add time, and an SMR drive can multiply it. Start promptly, keep load light and use CMR drives.
Last verified July 22, 2026 · 2 official sources checked Updated
This is a floor, not a promise: it assumes the drive reads or writes flat-out at the rate you set, with nothing else happening. Real rebuilds run longer — parity computation, using the NAS during the rebuild, and drive throttling all add time, and an SMR drive can multiply it. Sustained rates for current 3.5-inch NAS drives run roughly 180–280 MB/s (see each drive’s datasheet); 200 MB/s is a reasonable middle default.
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The honest answer is a range: here is the floor from the arithmetic, then the reasons reality is slower.
The theoretical floor
A rebuild reads or writes across the whole drive, so capacity ÷ sustained transfer rate is the fastest it could possibly finish. Current 3.5-inch NAS drives publish sustained rates of roughly 180–280 MB/s. An 8 TB drive: 8,000,000 MB ÷ (180–280 MB/s) ≈ 8–12 hours as a floor. Adjust the rate in the estimator above for your specific drive.
Why real rebuilds run longer
- Parity computation adds work beyond a flat copy.
- Using the NAS during the rebuild slows it.
- Throttling keeps the array responsive at the cost of speed.
- SMR drives can multiply the time or stall.
Why it matters
A single-parity array has no fault tolerance during the rebuild, so a second failure loses the pool. Start immediately, keep load light, use CMR, and consider RAID 6 / SHR-2 on larger arrays. The table lists in-stock 8 TB CMR drives by price per terabyte.
8 TB CMR drives, by CA$/TB
Live Amazon.ca prices in CAD, ranked by price per terabyte. The Recording column is verified against manufacturer documentation.
Related questions
Sources
Every technical claim on this page is checked against manufacturer and standards documentation. Dates are when each source was last reviewed.
- Seagate — IronWolf Pro datasheet (Max Sustained Transfer Rate OD, up to ~285 MB/s) — checked 2026-07-22
- Synology KB — Repair a Storage Pool — checked 2026-07-22