TBW (Terabytes Written) is a specification that indicates the total amount of data an SSD (solid state drive) can write over its lifetime before wearing out. It refers to the total terabytes of data that can be written to an SSD before it can no longer reliably store and rewrite data due to flash memory degradation. The higher the TBW rating, the more writes an SSD can handle before performance and reliability start to deteriorate. TBW provides an estimate of an SSD’s endurance and longevity – how much data can be written before the drive becomes unusable. It is one of the key factors to consider when selecting an SSD, as it determines the workload capacity and lifespan of the drive.
TBW ratings are important because flash memory cells in SSDs can only be erased and rewritten a finite number of times before they wear out. Each cell gradually degrades with use which eventually leads to read/write errors and failure. TBW specifies approximately how much data can be written before this occurs, allowing consumers to match SSD endurance to their projected workloads and data rewrite needs.
Typical TBW Ratings
TBW (terabytes written) is a measure of endurance for SSDs and represents the total amount of data that can be written to the drive before it is likely to fail. Consumer SSDs typically have TBW ratings ranging from 150 TBW on lower-end SATA SSDs to 600+ TBW on high-performance PCIe/NVMe models.
SATA SSDs in the 2.5″ form factor often have lower TBW ratings around 150-300 TBW for mainstream models and up to 500 TBW on prosumer drives. M.2 SATA SSDs have comparable ratings to 2.5″ SATA. However, high-performance NVMe M.2 SSDs using PCIe can offer 800-1000+ TBW thanks to advanced 3D NAND flash memory and other endurance enhancements.
In general, NVMe SSDs have much higher endurance than SATA, and prosumer/enterprise drives rated for heavy workloads exceed typical consumer-grade models. But even within the same interface, TBW ratings can vary significantly based on factors like NAND type and controller design.
Real-World Endurance
Manufacturer ratings for total bytes written (TBW) often exceed real-world endurance for most consumers. According to one Reddit user, “Endurance is a factor of how much data can be written and the manufacturer will guarantee data integrity after removing power from the drive.” But for many home uses, SSDs can outlast their ratings by a large margin.
In a long-term SSD endurance test by TechReport, consumer-grade SSDs lasted past 700TB of writes, even when rated for just 70-80TBW. Heavy workloads with sustained writes per day are needed to approach manufacturer ratings. For casual users, lightly used SSDs may only have a few GB written per day, extending endurance.
On Tom’s Hardware forums, users reported SSDs continuing to work reliably after 2-5 years of moderate use, despite exceeding ratings. One user’s SSD lasted 7 years before failure. Real-world endurance depends heavily on write workloads and use cases. For light home use, most SSDs greatly outlast their TBW ratings.
Use Cases and Requirements
The endurance needs for an SSD can vary significantly depending on the workload and data requirements. Light workloads like boot drives and basic office computing typically require less endurance. Whereas heavy workloads like database servers, video editing, and other write-intensive applications require higher endurance ratings.
Business and enterprise users tend to have greater endurance needs compared to basic home and consumer use. For example, a boot drive in a home PC may only write 10-20GB per day, while a database server drive in an enterprise setting may write hundreds of gigabytes per day. The enterprise workload would require an SSD rated for a much higher TBW.
Understanding the use case is critical. A Boot drive or light home use may only require 100 TBW or less. While a heavy write application may need 1800 TBW or more for guaranteed drive endurance over the warranty period. Matching the SSD to the workload helps prevent premature wear-out and ensures reliable performance.
Sources:
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/collateral/tech-brief/tech-brief-matching-ssd-endurance-to-common-enterprise-applications.pdf
Exceeding Ratings
When an SSD exceeds its rated TBW limit, it does not necessarily mean immediate failure or data loss. Many SSDs continue to operate past their official endurance rating. However, the risk of failure does increase over time as more data is written.
Studies have shown SSDs may continue working up to 2-3x past their TBW rating before failure occurs. However, there is no guarantee of this. The SSD will enter a read-only protection mode once the spare blocks are exhausted, preventing further writes. At this point data recovery is still possible if you power off the drive and use data recovery software.
If the SSD has completely failed, more intensive data recovery methods may be required. This involves removing the NAND flash chips and reading them directly using specialized equipment. However, there is no guarantee of recovering all the data this way.
The best option is to replace the SSD once it reaches 70-80% of its rated TBW. This provides a safety margin to account for unforeseen write operations. Regular backups are also essential in case failure does occur unexpectedly.
Improving Endurance
There are several ways to improve the endurance and extend the lifespan of an SSD drive.
One factor is the controller technology used in the SSD. Some controllers are designed with endurance in mind and implement techniques like advanced error correction to allow for more writes before failure. For example, controllers with LDPC error correction tend to offer improved endurance over cheaper controllers using BCH error correction.
Overprovisioning the SSD is another way to extend endurance. Having spare capacity allows the drive to better distribute writes and engage in wear leveling across more NAND cells. Typically, SSDs with higher overprovisioning ratings will last through more write cycles before failure. Consumer drives are often overprovisioned around 7-25%, while datacenter drives may be overprovisioned up to 70%.
Firmware optimizations and caching algorithms can also help improve endurance. For example, SandForce controllers use real-time data compression and deduplication to minimize the amount of data actually written to the NAND cells. This preserves the drive by reducing unnecessary write operations.
Sources:
https://ssdbuddy.com/category/guide/ssd-endurance-guide/
New Technologies
There are several emerging technologies that promise to further extend SSD endurance and lifespan moving forward. For example, newer 3D NAND flash memory architectures like QLC (quad-level cell) allow for increased memory densities while maintaining endurance. Multi-level cell flash is able to store more bits per cell by varying the voltage states, allowing higher capacities without more cells. As reported by StoragePartsDirect, “Technological breakthroughs such as 3D NAND have facilitated increased memory densities while improving reliability and endurance.”1
In addition, new interconnect technologies like PCIe 4.0 double the bandwidth compared to PCIe 3.0, allowing faster transfer speeds. As detailed by Embedded.com, Swissbit’s new N3202 PCIe 4.0 SSD “delivers reliability and endurance for various applications, including data logging, and edge servers.”2 Faster interfaces will help to fully utilize the potential of high-speed NAND flash.
Looking ahead, newer technologies like Z-NAND, computational storage, and storage class memory promise to significantly extend endurance and lifespan compared to current SSDs. With continual advances in 3D NAND, controllers, DRAM caching, and interfaces, future SSDs are projected to last substantially longer while providing faster performance.
Manufacturer Ratings
Manufacturer endurance ratings provide an estimate for how much data can be written to an SSD before performance degrades or data loss occurs. However, these ratings vary significantly between brands and should be interpreted cautiously
Brands like Samsung and Intel tend to provide more conservative ratings, while some other brands are accused of inflating the ratings to appear more durable. For example, according to reviews on Reddit, SSDs from companies like Crucial and Kingston sometimes fail before reaching the rated endurance 1.
In general, manufacturer ratings have increased over time, with the transition to larger capacities and 3D NAND technology. However, the way endurance is calculated has also changed, making direct comparisons difficult. For example, drive writes per day (DWPD) estimates may be provided instead of total terabytes written (TBW) for enterprise SSDs.
When evaluating ratings, it’s important to consider real-world usage. Most consumer workloads don’t come anywhere close to exceeding modern SSD endurance limits. However, for write-intensive applications like video editing, surveillance or database workloads, the higher TBW and DWPD ratings of “endurance” SSDs may provide extra peace of mind.
Extending SSD Life
There are several ways to extend the usable lifespan of an SSD even with heavy write workloads. Here are some tips:
Minimize Writes
Avoid unnecessary writes by tweaking system settings, using RAM disks for temporary files, disabling features like search indexing or hibernation, and configuring applications to reduce writes where possible.
Use SSD Monitoring Tools
Monitor your SSD’s health and remaining endurance using tools like SSDLife to get alerts when action is needed. This allows you to proactively manage the drive.
Backup Frequently
Regular backups are essential in case of premature SSD failure. Back up important data either periodically or continuously to another drive or the cloud. This ensures no data loss if the SSD wears out sooner than expected.
With proactive monitoring, write minimization, and backups, an SSD’s usable lifetime can be extended significantly beyond the rated TBW. Careful usage and maintenance allows the SSD to remain fast and reliable even with heavy workloads.
Conclusion
In summary, 300 TBW is generally enough endurance for most typical consumer use cases, but may fall short in certain professional/enterprise scenarios or for users who write extremely large amounts of data consistently. Looking at real-world SSD endurance tests, most modern drives exceed their rated TBW before failure, some by 2-4x or more. However, there are also examples of SSDs failing before or around their rated TBW as well. For most mainstream users, 300 TBW provides a reasonable useful lifespan of 5+ years under normal usage.
For demanding professional use cases like video editing, servers, or other write-intensive needs, a higher TBW rating of 600-1800+ may be required to ensure the SSD lasts through its warranty period. As SSD capacity increases, TBW also tends to scale up proportionally. Newer technologies like 3D NAND, ZNS SSDs, SLC caching, and advanced wear leveling algorithms continue to improve endurance. While ratings provide a basic guideline, real-world endurance can vary based on usage patterns. The best practice is still to buy from quality manufacturers and choose an appropriate TBW rating with headroom beyond your estimated requirements.