The following enterprise / data-center class HDDs are suitable for a RAID 6 NAS used for backup of code repositories and proprietary data. Models were chosen with Backblaze drive-stat reports in mind (low annualized failure rates and significant fleet sizes where possible), prioritizing reliability over maximum throughput.
| Manufacturer | Model / SKU | Capacity | Form Factor & Interface | RPM / Recording | Workload & Warranty | Backblaze reliability notes* | Comments (NAS use) | Vendor links (examples) |
|---|---|---|---|---|---|---|---|---|
| HGST (WD) |
MegaScale DC 4000.B HMS5C4040ALE640 |
4 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
~5700 RPM “Coolspin” CMR |
Data‑center / cold‑storage oriented Typically 3‑year warranty (varies by channel) |
Backblaze’s 2020 annual report shows this model at an AFR around 0.27 % over large numbers of drives and drive‑days, making it one of the best‑performing 4 TB models in their fleet. Subsequent 2024–2025 reports highlight it with repeated zero‑failure quarters and many drives approaching 10 years of continuous service. | Extremely strong long‑term field record; an excellent 4 TB choice when reliability is primary and performance demands are modest (backup / NAS). |
Newegg Amazon |
| HGST (WD) |
MegaScale DC 4000.B HMS5C4040BLE640 |
4 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
~5700 RPM “Coolspin” CMR |
Data‑center / NAS‑oriented variant Typically 3‑year warranty (varies) |
Backblaze groups this model with the ALE640 variant, reporting an AFR also around 0.27 % in 2020 and consistently low failure rates in later reports. It is considered one of the most reliable small capacity drives they operate. | Near‑identical reliability story to the ALE640; suitable to mix in the same array if you cannot get all drives with the exact same suffix, though identical models are still ideal. |
Amazon search eBay |
| Toshiba |
Surveillance / MD04 Series MD04ABA400V |
4 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
~5400 RPM “low‑spin” CMR |
Surveillance / 24×7 video workload Typically 2–3‑year warranty (varies) |
In Backblaze’s Q2 2020 report this model recorded zero failures for the quarter, and its annualized AFR across 2020 is reported in external summaries as being in the same low range (~0.3 %) as the best HGST models, albeit with a smaller fleet. | Designed for continuous write‑heavy surveillance use; performance is modest but well‑suited to a backup NAS and log/archival workloads. A solid 4 TB option if priced better than the HGST drives in your market. |
GoHardDrive HardDiskDirect |
| Manufacturer | Model / SKU | Capacity | Form Factor & Interface | RPM / Recording | Workload & Warranty | Backblaze reliability notes* | Comments (NAS use) | Vendor links (examples) |
|---|---|---|---|---|---|---|---|---|
| Seagate |
Exos 7E8 ST8000NM000A |
8 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR |
Enterprise / bulk‑storage drive Workload up to ~550 TB/yr 5‑year limited warranty (Exos line) |
Backblaze repeatedly highlights this model as an outstanding performer: multiple quarters and the entire 2023 year with zero failures, and a lifetime AFR reported as effectively 0 % through early 2024 over more than 100k drive‑days. It is one of their most reliable drives overall. | Top‑tier 8 TB choice for a reliability‑first RAID 6 NAS. Capacity per bay is lower than 16 TB options, but you gain from an excellent field reliability record and can use more spindles for IOPS and resiliency. |
Amazon Newegg |
| HGST (WD) |
Ultrastar He8 HUH728080ALE600 |
8 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR, helium‑filled |
Enterprise / data‑center Workload up to ~550 TB/yr Typically 5‑year warranty (Ultrastar line) |
Backblaze’s 2020 analysis cites this model with an AFR of about 0.29 %, placing it among the most reliable drives they use; Q2 2020 specifically recorded zero failures for this model. Later reports note a gradual AFR increase with age, but still at a level that compares favorably to many other 8 TB drives. | A very strong 8 TB enterprise choice, especially if you prefer HGST/WD. Helium design offers good power and acoustic characteristics, and Backblaze’s data supports its use for long‑term NAS storage. |
Newegg Amazon |
| Seagate |
Exos 7E8 (Enterprise Capacity v5) ST8000NM0055 |
8 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR |
Enterprise drive, up to ~550 TB/yr workload 5‑year limited warranty (enterprise line) |
Earlier Backblaze reports (2016–2018) showed this model with very low AFR (well under 1 %) and even zero failures in its first year of deployment. Over a longer horizon, newer analyses put its AFR around the low single‑digit percent range (≈1–2 %), still acceptable but not as exceptional as ST8000NM000A or HUH728080ALE600. | A reasonable 8 TB enterprise option if priced attractively or if availability of ST8000NM000A / HUH728080ALE600 is limited. For a strictly reliability‑first build, prefer the two models above, but mixing this in the same array is still defensible. |
Newegg Amazon |
Any of the 16 TB models below can comfortably exceed 16 TB usable capacity in RAID 6. For example, 6×16 TB in RAID 6 provides roughly 64 TB raw and (6−2)=4 disks worth of usable capacity (~64 TB minus formatting/overhead), with two additional identical drives used as hot spares.
| Manufacturer | Model / SKU | Capacity | Form Factor & Interface | RPM / Recording | Workload & Warranty | Backblaze reliability notes* | Comments (NAS use) | Vendor links (examples) |
|---|---|---|---|---|---|---|---|---|
| Seagate |
Exos X18 ST16000NM002J |
16 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR (conventional magnetic recording) |
Enterprise drive, typical rating up to ~550 TB/yr workload 5‑year limited warranty (per Seagate Exos line) |
Backblaze’s 2024 annual report singles this model out:
only one failure in the year, AFR ≈ 0.22 %,
one of the best-performing large-capacity drives in their fleet
(tens of thousands of drive‑days). Also appears with repeated zero‑failure quarters in recent quarterly stats. |
Excellent candidate for a reliability‑first RAID 6 NAS. High capacity with a very strong field record in Backblaze’s environment. Good choice as the “primary” model if you want all drives identical. |
Newegg DiscTech |
| Western Digital |
Ultrastar DC HC550 WUH721816ALE6L0 |
16 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR; helium‑filled |
Enterprise / data‑center drive, typical rating up to ~550 TB/yr 5‑year limited warranty (Ultrastar line) |
Backblaze’s 2021 stats report AFR ≈ 0.14 % for this model with growing drive‑days, and later Q3 2022 data shows zero failures that quarter with sufficient fleet size to be meaningful. It is repeatedly highlighted as one of the best‑performing high‑capacity HDDs in their farm. | Very strong reliability track record; an excellent alternative to the Seagate Exos X18 if you prefer WD. Using this as your main 16 TB choice would also comfortably exceed your 16 TB usable RAID 6 requirement. |
Amazon Newegg |
| Toshiba |
MG08 Series MG08ACA16TE |
16 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR; helium‑filled 9‑platter design |
Enterprise / nearline HDD Workload up to ~550 TB/yr 5‑year limited warranty (MG series) |
Backblaze’s 2021 drive‑stats report AFR in the ~0.9–1.1 % range for this model (e.g. 0.91 % AFR with thousands of drives in service), i.e. still comfortably below their overall fleet average AFR. | Solid enterprise‑class option from Toshiba. Slightly higher AFR than the very best Seagate/WD 16 TB models in Backblaze’s numbers, but still a strong reliability profile and good capacity‑per‑slot for a backup NAS. |
Newegg ServerPartDeals |
| Seagate |
Exos 7E8 ST8000NM000A |
8 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR |
Enterprise / bulk‑storage drive Workload up to ~550 TB/yr 5‑year limited warranty (Exos line) |
Backblaze repeatedly highlights this model as an outstanding performer: multiple quarters and the entire 2023 year with zero failures, and a lifetime AFR reported as ~0.0 % through early 2024 (with well over 100k drive‑days). It’s one of their most reliable drives overall. | Capacity is lower per bay, but reliability is exceptional based on Backblaze data. For example, 6×8 TB in RAID 6 yields ~32 TB usable, leaving plenty of room above your 16 TB minimum and giving you the option to use more, smaller drives for resiliency. |
Amazon Newegg |
| Western Digital |
Ultrastar DC HC530 WUH721414ALE6L4 |
14 TB |
3.5″ HDD SATA 6 Gb/s, 512e |
7200 RPM CMR; helium‑filled |
Enterprise / data‑center HDD Workload up to ~550 TB/yr 5‑year limited warranty (Ultrastar line) |
Backblaze reports consistently low AFR for this model; external summaries of their data put the AFR in the ~0.16–0.32 % range over large fleets (thousands of drives, millions of drive‑days) — making it one of the better‑behaved 14 TB drives in their environment. | Slightly lower per‑drive capacity than 16 TB, but still very strong on reliability. 6×14 TB in RAID 6 yields about 56 TB raw and 4×14 TB worth of usable capacity, easily above your 16 TB minimum. Good choice if 14 TB pricing is more favorable in your market. |
Amazon Newegg |
*Backblaze statistics are based on drives deployed in their data centers and are best used to compare models relative to each other. Data should be interpreted as empirical field data under that workload; they are not formal guarantees of future performance, but they provide useful guidance on relative reliability when selecting drives for a reliability‑first RAID 6 NAS.
Practical build note: for a RAID 6 array with two hot spares and a minimum of 16 TB usable, a common pattern would be 6 active drives (e.g. 6×16 TB HC550 or Exos X18) in RAID 6 plus 2 identical hot spares. This yields (6−2)=4 drives worth of usable capacity and keeps replacement simple.