Backblaze identified the best and worst HDDs: the average failure rate in 2025 dropped to 1.36%.

Backblaze publishes HDD failure results for Q4 2025

The cloud storage company Backblaze released statistics on hard disk drive (HDD) failures for the last quarter and the entire year. The report includes nearly 350,000 drives – just 30 models.

1. Quarterly overview (Q4 2025)
Parameter Data Total number of HDDs 337,192 (after excluding some units) New models introduced into service
• Seagate ST16000NM000J – 112 units (16 TB)
• WDC WUH722626ALE6L4 – 1,201 units (26 TB, first drive of that capacity)

Failures in the quarter | Model | Capacity | Number of failures

| HGST HMS5C4040BLE640 (4 TB) | 1 |
| Seagate ST12000NM000J (12 TB) | 1 |
| Seagate ST16000NM000J (16 TB) | 1 |
| WDC WUH722626ALE6L4 (26 TB) | 1 – in the first quarter of operation |

Reliable models:

- Seagate ST8000NM000A (8 TB) – 0 failures
- Seagate ST16000NM002J (16 TB) – 0 failures

Worst-performing models:

| Model | AFR (average annual failure rate) |
| HGST HUH728080ALE600 (8 TB) | 10.29 % |
| Seagate ST10000NM0086 (10 TB) | 5.23 % |
| Toshiba MG08ACA16TEY (16 TB) | 4.14 % |

- HGST HUH728080ALE600 triggered an investigation: temperature was ruled out, vibration was identified as the culprit. Backblaze plans to gradually retire this model from service without additional fixes.
- Toshiba MG08ACA16TEY showed a high AFR in the previous quarter due to firmware updates; its level remains above average but is already decreasing.

2. Annual summary (2025)
Metric Value Total number of HDDs 344,196 (30 models) Average annual AFR 1.36 % (down from 1.55 % in 2024)

- No model reported zero failures for the year, but many had fewer than two failures per quarter:
- HGST HMS5C4040BLE640 – 5 failures
- Seagate ST12000NM000J – 4
- Seagate ST14000NM000J – 7
- Seagate ST16000NM002J – 1
- Toshiba MG09ACA16TE – 3
- WDC WUH722626ALE6L4 – 1

- Distribution by capacity (Q4 2025):
- ≤12 TB – 25.13 %
- 14–16 TB – 52.06 %
- >20 TB – 22.81 %

3. Year-over-year comparison (AFR)
Year AFR
2023 1.70 %
2024 1.57 %
2025 1.36 % (repeat of the 2022 level)

These data are based on models that, as of December 31 2025, had been in service for ≥250 units and had operated for more than 50,000 days.

4. Long-term reliability
Backblaze compiled statistics on HDDs that, by December 31 2025, had at least 500 units and over 100,000 operating days. The overall AFR across the entire history of operation is 1.30 % and has remained stable for several quarters.

Conclusion – Overall, fleet resilience improved: the annual AFR dropped almost 0.2 %.
- Some models (especially HGST HUH728080ALE600) require attention; others show very low failure rates.
- Backblaze continues monitoring and gradually adjusts its drive mix in line with reliability metrics.