How long does it take to rebuild a 12TB drive in a NAS?
As a theoretical floor, a 12TB drive read or written flat-out at 180–260 MB/s sustained takes roughly 13–19 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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At 12 TB the numbers get long enough that the second-failure risk during the rebuild becomes the real story. Start with the floor, then the caveats.
The theoretical floor
Capacity ÷ sustained transfer rate is the fastest a rebuild could possibly finish. Current 3.5-inch NAS drives publish sustained rates around 180–260 MB/s. A 12 TB drive: 12,000,000 MB ÷ (180–260 MB/s) ≈ 13–19 hours as a floor. The estimator above defaults to 12 TB: change the rate to match your drive's datasheet.
Why real rebuilds run longer
- Parity computation for RAID 5/6/SHR is extra work.
- Concurrent use of the NAS slows the rebuild.
- Throttling trades speed for responsiveness.
- SMR drives can turn this into days.
Why it matters
A 12 TB single-parity rebuild can take the best part of a day with no fault tolerance the whole time: a second drive failing loses the pool. At this capacity, RAID 6 / SHR-2 is worth it: double parity survives a failure during the long rebuild. Use CMR drives and start promptly. The table lists in-stock 12 TB CMR drives by price per terabyte.
12 TB CMR drives, by CA$/TB
Live Amazon.ca prices in CAD, ranked by price per terabyte. The Recording column is verified against manufacturer documentation. Prices checked
| Model | Capacity | Recording | Price | CA$/raw TB | |
|---|---|---|---|---|---|
 Seagate Exos X22 22TB SATA 6Gb/s 7200RPM 3.5" Enterprise Hard Drive - ST22000NM001ENewbest price per TB CMR recording, SATA enterprise drive Amazon.ca · sold by ServerPartDeals · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,108Buy on Amazon | 22 TB | CMR ✓ | CA$1,108 | CA$50.38/TB | Buy on Amazon |
 Seagate IronWolf Pro 32TB Enterprise NAS Internal HDD Hard Drive – CMR 3.5 Inch SATA 6Gb/s 7200 RPM 512MB Cache for RAID Network Attached Storage, Rescue Services (ST32000NTZ00)New CMR recording, SATA NAS drive rated for 24/7 use Amazon.ca · sold by THEKEYKEY · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,740Buy on Amazon | 32 TB | CMR ✓ | CA$1,740 | CA$54.37/TB | Buy on Amazon |
 Seagate Exos M 28TB Enterprise Internal Hard Drive HDD - 3.5in 6GB/s SATA 7200RPM 2.5M MTBF (ST28000NM003K)New CMR recording, SATA enterprise drive Amazon.ca · sold by Amazon.ca · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,543Buy on Amazon | 28 TB | CMR ✓ | CA$1,543 | CA$55.11/TB | Buy on Amazon |
 Seagate Exos X24 ST20000NM002H 20TBNew CMR recording, SATA enterprise drive Amazon.ca · sold by THEKEYKEY · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,165Buy on Amazon | 20 TB | CMR ✓ | CA$1,165 | CA$58.25/TB | Buy on Amazon |
 Western Digital HUH721212ALE604 12TB Ultrastar DC HC520 SATA HDD - 7200 RPM Class, SATA 6 Gb/s, 256MB Cache, 3.5"New CMR recording, SATA enterprise drive Amazon.ca · sold by Seller_King · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$699Buy on Amazon | 12 TB | CMR ✓ | CA$699 | CA$58.25/TB | Buy on Amazon |
 Seagate Exos X24 24TB Enterprise Internal Hard Drive HDD - 6GB/s SATA 7200RPM 2.5M MTBF (ST24000NM002H)New CMR recording, SATA enterprise drive Amazon.ca · sold by THEKEYKEY · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,400Buy on Amazon | 24 TB | CMR ✓ | CA$1,400 | CA$58.33/TB | Buy on Amazon |
 Seagate IronWolf Pro 20TB Enterprise NAS Internal HDD Hard Drive – CMR 3.5 Inch SATA 6Gb/s 7200 RPM 256MB Cache for RAID Network Attached Storage, Rescue Services (ST20000NTZ01/ST20000NT001)New CMR recording, SATA NAS drive rated for 24/7 use Amazon.ca · sold by THEKEYKEY · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,235Buy on Amazon | 20 TB | CMR ✓ | CA$1,235 | CA$61.75/TB | Buy on Amazon |
 Western Digital 22TB WD Red Pro NAS Internal Hard Drive HDD - 7200 RPM, SATA 6 Gb/s, CMR, 512 MB Cache, 3.5" - WD221KFGXNew CMR recording, SATA NAS drive rated for 24/7 use Amazon.ca · sold by Deals2You · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,400Buy on Amazon | 22 TB | CMR ✓ | CA$1,400 | CA$63.64/TB | Buy on Amazon |
 Seagate IronWolf 16TB NAS Internal Hard Drive HDD – CMR 3.5 Inch SATA 6GB/S 7200 RPM 256MB Cache for Raid Network Attached Storage, with Rescue Service (ST16000VN001)New CMR recording, SATA NAS drive rated for 24/7 use Amazon.ca · sold by MAPOGO LION LLC · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,028Buy on Amazon | 16 TB | CMR ✓ | CA$1,028 | CA$64.25/TB | Buy on Amazon |
 Western Digital 16TB WD Red Pro NAS Internal Hard Drive HDD - 7200 RPM, SATA 6 Gb/s, CMR, 256 MB Cache, 3.5" - WD161KFGXNew CMR recording, SATA NAS drive rated for 24/7 use Amazon.ca · sold by Amazon.ca · one bare internal drive; shipping and taxes not included · checked Oct 7, 2026CA$1,060Buy on Amazon | 16 TB | CMR ✓ | CA$1,060 | CA$66.25/TB | Buy on Amazon |
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)