Solid state drives (SSDs) have become increasingly popular in computers over the past decade thanks to their fast speeds and reliability compared to traditional hard disk drives (HDDs). However, SSDs are not infallible, and they can and do fail from time to time. So how often do SSDs actually go bad?
What is an SSD?
An SSD, or solid state drive, is a type of computer storage device that uses flash memory to store data persistently. Unlike a traditional HDD, an SSD has no moving parts – instead of a mechanical arm moving to different parts of a magnetic platter to read and write data, an SSD accesses data electronically from flash memory chips. This gives SSDs two major advantages over HDDs:
- Faster access speeds – SSDs can read and write data much faster than HDDs can, often by a factor of 100x or more for sequential access.
- Increased reliability – With no moving parts and greater resistance to shocks and vibration, SSDs are less prone to mechanical failure over time.
However, SSDs do still have a limited lifetime. Data can only be written and erased from flash memory chips a finite number of times before they begin to fail. This lifespan limitation is a downside of SSDs compared to HDDs, which can often last for 5 years or more of continuous use before mechanical failure occurs.
What Determines SSD Lifespan?
There are several factors that influence how long an SSD will last before reaching the end of its write cycle lifespan:
- Total bytes written – The total amount of data written to the SSD over its lifetime is the primary determinant of lifespan. The more data written, the faster it will reach its write cycle limit.
- Wear leveling algorithms – The SSD controller uses these to spread writes across all flash cells evenly. Better algorithms extend lifespan.
- Over-provisioning – Extra flash capacity set aside to replace failed cells. More over-provisioning equals more writes allowed.
- Drive writes per day (DWPD) – An SSD spec indicating its daily write workload capacity. Consumer models often 1-3 DWPD, datacenter models 5-10 DWPD.
In addition, operating conditions affect SSD longevity. High temperatures, voltages outside specs, and vibration all accelerate wear and reduce lifespan. But under normal conditions, the write workload is generally the primary factor.
Typical Lifespan of Consumer SSDs
Most consumer-grade SSDs today use 3D TLC NAND flash memory and are designed for 1-3 DWPD workloads. Many manufacturers do not provide official lifespan ratings, but based on technical analysis of common SSDs:
- 128GB-256GB drives often last for 150-300 TBW (terabytes written)
- 512GB-1TB models reach 300-600 TBW
- High-end consumer 2-4TB drives over 1000 TBW
Heavy PC users write 10-40 GB per day, while light users may write only 2-5 GB daily. At 20 GB per day writes, a 512GB SSD with 300 TBW endurance would last:
300 TBW / 20 GB per day = 15,000 days = 41 years
Even for heavy 50 GB per day workloads, this SSD would last over 5 years. Consumer SSDs typically outlive the usable lifespan of the computer they are installed in.
Lifespan in Heavy Enterprise/Datacenter Use
In datacenters and enterprise environments with highly write-intensive workloads, SSDs configured for higher 5-10+ DWPD are used. These specialized datacenter SSDs are engineered for greater endurance:
- 800 GB-1.6 TB models often 2,000 – 3,000 TBW
- 3.2 TB-6.4 TB models 4,000 – 10,000 TBW
- High capacity over 8 TB nearing 20,000 TBW
Even at extremely heavy workloads of 100 GB daily writes, a 1.6 TB enterprise SSD with 3,000 TBW endurance would last over 8 years. Actual lifespans in datacenters are often longer than this specification as workloads are not sustained at peak writes indefinitely.
SSD Failure Rate Statistics
While SSDs have finite write cycle lifespans, most do not actually reach the point of failure due to wearing out. Studies of large SSD populations in datacenter environments have shown annual failure rates under 2%:
- Google: 1.7% (2014 study of over 30,000 consumer-grade SSDs)
- Facebook: 1.33% (2014 study of over 100,000 flash storage drives)
- Microsoft: 1-2% (2015 study of over 1 million SSDs)
Note these failure rates include all causes of failure, including infant mortality or due to non-endurance related faults. Actual permanently worn out SSDs were extremely rare, indicating most drives do exceed their rated endurance limits.
SSD Lifetime Failure Rate by Years of Use
| Years in Use | Failure Rate % |
|---|---|
| 1 | 1.5% |
| 2 | 2.1% |
| 3 | 2.6% |
| 4 | 3.0% |
| 5 | 3.4% |
| 6 | 3.9% |
Failure rates increase gradually over time, but remain under 4% even after 5-6 years of service. Functional SSD failure due to complete wear out remains negligible, with most failures due to non-endurance issues.
SSD Failure Mode Statistics
While SSD lifetime wear-out failures are rare, when SSDs do fail it is important to understand the most common failure modes. The following table summarizes common SSD failure modes based on datacenter studies:
| Failure Mode | Percentage |
|---|---|
| Firmware crashes/boot failure | 25% |
| Bad blocks/lost data | 20% |
| Electrical issues | 15% |
| Failed/disconnected | 14% |
| Wear out/write limit | 3% |
| Overheating | 2% |
Firmware bugs, electrical faults, and bad block management account for a majority of all SSD failures. True end-of-life write exhaustion failures remain amongst the least common at around 3%.
SSD Failure Rate Compared to Hard Disk Drives
Although SSDs do have a finite lifespan and gradual failure rate increase with age, they are still much more reliable than traditional hard disk drives (HDDs). HDDs have many more components and moving parts vulnerable to mechanical failure. Enterprise HDD studies show failure rates of 4-10% annually compared to the 1-2% SSD rates.
Even for drives that have been in operation for 5+ years, HDDs have 3-4X higher failure rates compared to SSDs. With no moving parts to wear out, SSDs are fundamentally more resilient to physical failure over time.
Factors That Can Decrease SSD Lifespan
While SSDs are designed to last years even under heavy write workloads, there are some factors than can potentially shorten their usable lifespans:
- Cheap low-quality NAND – Cutting corners on NAND quality leads to fewer program/erase cycles.
- Insufficient over-provisioning – Without spare area for wear leveling, cells wear out faster.
- Excessive overheating – Heat accelerates all failure mechanisms in SSDs.
- Low-quality controller – Crucial for managing NAND wear leveling and error correction.
- Excessive sequential writes – High sustained traffic to a small number of cells.
Buying SSDs from reputable manufacturers helps avoid low-quality components that can shorten lifespan. Proper cooling and monitoring SSD health stats like total data written and wear leveling counts can also help maximize lifespan.
Extending SSD Lifespan
The expected lifespan of most SSDs exceeds the usable lifespan of the system they are installed in. However, in more demanding datacenter/enterprise contexts, it may be desirable to extend SSD lifespan even further. Tactics to optimize SSD endurance include:
- More over-provisioning – Configuring extra spare area than default extends writes allowed before wear-out.
- Accelerating wear leveling – Improves spreading of writes across all cells to avoid hot spots.
- Advanced NAND management – More sophisticated handling of NAND can improve endurance.
- Caching writes in RAM – Buffers flash writes to reduce total drive writes needed.
- Limiting sequential writes – Spreads out data accesses across more physical locations.
Newer generation NAND flash like 3D TLC also offer enhanced endurance over older planar technologies. But even most consumer SSDs well exceed the expected years of service, minimizing the need for extra endurance enhancements.
Conclusion
SSD reliability continues to improve, but all storage devices have a finite lifespan. For the average consumer SSD, expected lifetimes are 5 years or more even under heavy write workloads. Newer advances in 3D NAND have increased endurance as well. In datacenter deployments, SSDs configured for higher workloads routinely function over 8 years before failures exceed a few percent.
Complete wear-out of flash cells through sheer writes is relatively uncommon, with electronics and firmware bugs causing the vast majority of SSD failures. Compared to mechanical hard disk drives, solid state drives have proven to be remarkably resilient over time. And continued NAND flash improvements promise to further enhance SSD reliability into the future.