What is SSD Endurance?
SSD endurance refers to how much data can be written to an SSD before it fails or wears out. It measures the total bytes written (TBW) over the lifetime of a solid state drive under normal usage conditions (Salvage Data). The endurance rating provides an estimate for the total drive writes (DW) an SSD can withstand before reaching its write endurance limit.
Endurance is a key specification for SSDs because NAND flash memory has a limited number of program/erase (P/E) cycles. Each cell within an SSD can only be written and erased a finite number of times before it wears out and can no longer reliably store data (TechTarget). The total P/E cycles determines the overall endurance and usable lifespan of an SSD.
A higher endurance rating indicates the SSD can withstand more writes over its lifetime before failure. Endurance gives consumers a way to compare SSDs and determine if a drive can reliably operate under their expected workloads. For write-intensive applications, choosing an SSD with high endurance is crucial for optimal performance and longevity (Western Digital Blog).
TBW Rating Explained
TBW stands for Terabytes Written. It is a metric used to measure the endurance of solid state drives (SSDs). The TBW rating specifies the total amount of data that can be written to an SSD before it is likely to fail or lose significant performance. It estimates how much data can be written over the entire lifetime of the SSD.
Most consumer SSDs today have TBW ratings ranging from 150 TBW to 600 TBW for higher capacity models. This means a 500 GB SSD with 300 TBW could withstand writing 150 terabytes per year for 2 years before reaching its limit. Typically enterprise-class SSDs have much higher TBW ratings of 1,500 TBW or more.
The TBW rating is derived through drive writes per day (DWPD) testing in controlled lab conditions. The total terabytes written during the test until failure determines the TBW rating. Real-world workloads may differ from these idealized tests.
While not a guarantee, the TBW specification provides an estimate of the total data written over the SSD’s lifespan before performance deteriorates or the drive fails. This helps assess the endurance and expected useful life of an SSD in heavy write environments.
How Endurance is Tested
SSD endurance is typically tested according to industry standards like JESD219 from JEDEC (Joint Electron Device Engineering Council). JESD219 defines specific workloads and testing methods for evaluating endurance of different SSD classes.
The test writes data repeatedly to the entire logical address space of the SSD until it reaches end of life failure. The total terabytes written before failure is the drive’s endurance rating or TBW. JESD219 uses workloads tailored to common real-world usage scenarios.
Vendors also conduct their own proprietary endurance testing. For example, Samsung uses a rigorous verification procedure with carefully controlled temperature and workload settings. Their tests write random data constantly until reaching the drive’s guaranteed TBW.
Both standard industry and custom endurance tests are designed to validate SSD lifespan under maximal stress. However, critics argue that short burst testing cannot replicate real-world conditions over months or years of uneven complex usage.
Real-World vs Lab Endurance
Lab testing conditions often overestimate the real-world endurance of SSDs. This is because lab tests subject SSDs to continuous writes at their full rated speeds in ideal conditions. However, real-world usage tends to be more varied with a mix of reads, writes, idle time, and bursty workloads [1]. Additionally, factors like operating temperature, power loss events, and firmware bugs can reduce SSD lifespan in the field [2].
For example, one real-world SSD endurance experiment found most consumer 120-160GB SSDs lasted only 1-4 years of average client workloads before failing, versus the 5-10 years estimated from lab endurance ratings [1]. Enterprise SSDs fared better at 3-7 years. This demonstrates lab testing does not capture real-world variability and risks that reduce SSD lifespan.
Therefore, real-world endurance tends to be 50-75% lower than suggested by manufacturer ratings from lab testing. When estimating SSD lifespan, one should discount lab endurance ratings accordingly based on expected real-world usage patterns and risks.
Monitoring SSD Wear
To monitor the amount of wear on your SSD over time, you can use free tools like SSDLife and CrystalDiskInfo. These tools provide detailed information about your SSD’s health and can estimate its remaining useful life.
SSDLife shows the total terabytes written (TBW) to your SSD along with a wear level indicator. Most consumer SSDs today have a TBW rating ranging from 100-600TB, with higher end drives having a rating of 1800TB or more. As you approach the rated TBW limit, the wear level indicator will turn from green to yellow to red. However, hitting this limit does not necessarily mean your SSD will fail immediately.
CrystalDiskInfo provides even more granular detail, showing the percentage of life remaining based on the manufacturer’s endurance testing as well as raw value SMART attributes like Total_LBAs_Written. You want to watch for high percentages of used reserve blocks, which indicates the SSD controller is swapping out bad cells. The Current Pending Sector count is also important – once reallocated sectors start appearing, it’s a sign your SSD is nearing the end of its useful life.
By periodically checking these values in SSDLife and CrystalDiskInfo, you can monitor your SSD’s wear over time and watch for signs of degradation. Just remember these tools provide estimates only – real world endurance depends on usage habits and the SSD’s quality.
Improving Endurance
There are a few techniques that can help improve the endurance and lifespan of an SSD.
Overprovisioning refers to configuring the SSD with more storage capacity than is exposed to the operating system. For example, using a 500GB SSD but only exposing a 450GB partition. This provides additional spare blocks for the controller to use when wear leveling [1]. Most SSDs come with some amount of overprovisioning from the factory.
Caching software like PrimoCache can help reduce writes by caching frequently written data in RAM rather than committing it to the SSD [2]. This helps absorb a lot of the small random writes that contribute heavily to wear.
Keeping the SSD firmware up to date can also help, as manufacturers will optimize wear leveling and garbage collection algorithms over time. Newer firmware versions may increase endurance.
Other tips include enabling TRIM, limiting redundant writes, avoiding excessive drive partitioning, and using the SSD’s built-in toolbox to check wear levels if available.
Endurance Considerations
The endurance rating of an SSD is most important for write-intensive workloads that repeatedly overwrite data. For example, databases, virtual machines, data analytics, video editing, and surveillance video storage all tend to rewrite the same cells frequently, wearing down the drive [1]. In these use cases, a higher TBW rating provides more protection against early failure.
For mainly read-focused workloads like booting an OS or loading games, endurance is less of a concern. The SSD still needs sufficient endurance to withstand some write amplification from activities like garbage collection, but ultra-high endurance is unnecessary [2].
In general, if the workload routinely overwrites more than 10% of the drive’s capacity per day, a higher TBW rating is advised. For lighter write workloads, moderate endurance is sufficient to reach the useful lifespan of the SSD.
SSD Failure Factors
While write endurance is often considered the primary factor in SSD reliability, there are other important factors that can lead to SSD failure in real-world usage:
According to research by Backblaze covering over 3,000 SSDs, the overall annual failure rate is around 0.89% per year across all SSD models [1]. This suggests that on average, consumer SSDs are highly reliable with low failure rates.
Some key factors besides write endurance that contribute to SSD failure include:
- Manufacturing defects – Even high-quality SSDs can have flaws from the manufacturing process.
- Controller failure – The SSD controller chip can fail even if NAND flash is still functional.
- External issues – Power surges, operating temperature, physical damage, etc.
- Wear levelling effectiveness – How evenly writes are distributed impacts wear.
In consumer applications, random write workloads and bursts of writes/rewrites are more damaging than sequential writes. Workstation usage with large files is gentler on SSDs versus running databases or virtual machines.
While lab endurance tests provide a baseline for SSD lifespan, real-world usage often exceeds rated endurance by a large margin. Proper SSD monitoring and maintenance helps avoid premature failure in most cases.
Extending SSD Lifespan
There are several techniques manufacturers use to extend the lifespan of SSDs beyond the baseline endurance rating:
- Wear leveling: The SSD controller spreads writes across all the blocks in the drive to avoid wearing out a small set of frequently used blocks. This helps distribute the wear and maximize overall drive endurance (The SSD Guy).
- Over-provisioning: SSDs reserve a portion of total capacity as spare area, allowing the controller to better manage wear leveling and replace worn out cells. 7-20% over-provisioning is common (The SSD Guy).
- TRIM: Enabling TRIM allows the OS to notify the SSD which blocks are no longer in use, preventing unnecessary writes. This reduces write amplification and increases endurance.
- Replacing early: Since SSDs tend to fail suddenly after reaching endurance limits, proactively replacing drives before reaching the rated TBW can avoid unexpected failures.
With proper firmware algorithms and some over-provisioning, quality SSDs can last for many years of typical consumer workloads. But under extremely write-intensive use cases, the drive may wear out sooner than the rated TBW.
The Future of SSD Endurance
SSD technology continues to advance, leading to improvements in endurance and lifespan. Newer technologies like MLC and TLC SSDs offer increased endurance compared to early single-level cell (SLC) SSDs. Whereas SLC SSDs lasted around 5 years, MLC SSDs can survive for up to 10 years of average use.
Estimates for the lifespan of future SSDs are improving as the technology matures. According to industry experts, we can expect the average SSD lifespan to reach 15-20 years within the next 5-10 years. Improved controller technology and advanced flash memory types like 3D NAND will extend the write endurance of SSDs.
New SSD form factors like M.2 and U.2 allow for better cooling, which also improves longevity. Techniques like machine learning are being used to optimize wear leveling and reduce write amplification that can degrade SSDs prematurely.
While mechanical hard disk drives may still outlive SSDs, the endurance gap is narrowing. For most consumer use cases, SSD lifespan is already sufficient and will only get better over time.