Solid state drives (SSDs) have become increasingly popular in computers and data centers due to their faster speeds and lower latency compared to traditional hard disk drives (HDDs). However, one key specification that is often overlooked is write endurance – how much data can be written to the drive before it wears out. In this comprehensive guide, we will examine the factors that affect SSD write endurance and explain what the average lifetime write endurance is for today’s SSDs.
What is SSD Write Endurance?
Write endurance refers to the amount of data that can be written to an SSD before it begins to wear out and lose the ability to reliably store data. This is generally measured in drive writes per day (DWPD) or total terabytes written (TBW) over the lifespan of the SSD.
NAND flash memory cells, which store data on SSDs, can only be written and erased a finite number of times before they start to break down. Each erase/write cycle causes a small amount of damage to the cells. After extensive use, enough cells may have degraded that the SSD starts to develop uncorrectable errors when reading/writing data.
Most consumer SSDs are rated for a TBW endurance ranging from 150 TBW on the low end to 600 TBW or more on high-end models. For enterprise/datacenter SSDs which need higher endurance, drive writes per day are commonly used. DWPD ratings of 1-3 are typical for read-intensive enterprise workloads, while DWPD ratings of 5-10+ are seen on SSDs meant for write-intensive uses like caching or logging.
Factors That Affect SSD Endurance
There are several key factors that determine the write endurance characteristics of an SSD:
- NAND flash type – SLC NAND has the highest endurance, followed by MLC, TLC, and QLC. The more bits stored per cell, the lower the endurance.
- Process node size – Smaller process nodes generally have lower endurance. For example, a 64-layer 3D NAND SSD will typically have higher endurance than a 96-layer 3D NAND SSD.
- Over-provisioning – Having a larger percentage of spare flash capacity set aside improves endurance by allowing more space for wear leveling algorithms.
- Wear leveling algorithms – The effectiveness of the controller at evenly distributing writes across all cells impacts overall SSD endurance.
- Intended usage – Consumer/client SSDs are designed for lighter workloads and have lower endurance ratings than SSDs designed for heavy write-intensive enterprise work.
What is the Average Endurance of a Consumer/Client SSD?
For today’s client/consumer SSDs using 3D TLC NAND flash, the average write endurance rating is around 300-500 TBW for a standard 500GB-1TB capacity drive. Here are some examples from popular consumer SSD models:
- Samsung 870 EVO SATA SSD: 600 TBW (1TB model)
- Samsung 980 Pro PCIe 4.0 NVMe SSD: 600 TBW (1TB)
- WD Blue SN570 NVMe SSD: 300 TBW (1TB)
- Crucial P5 PCIe 3.0 NVMe SSD: 360 TBW (1TB)
- Intel 670p QLC NVMe SSD: 185 TBW (1TB)
Lower capacity drives generally have proportionally lower endurance ratings. The main exceptions are entry-level and budget SSDs which often have reduced endurance specifications across all capacities to help cut costs.
Based on this sample, we can conclude that most mid-range and high-end consumer SSDs have an average write endurance in the 300-600 TBW range for 1TB models, or around 0.3-0.6 drive writes per day (DWPD) over a typical 5 year warranty period.
Write Endurance of Enterprise/Data Center SSDs
Enterprise and data center SSDs need to withstand much higher write workloads than typical consumer SSDs. Endurance is measured using drive writes per day (DWPD) based on a full capacity fill per day.
Here are some typical DWPD endurance specifications of enterprise SSDs using TLC NAND flash:
- Read-optimized enterprise SSDs: 1-3 DWPD
- Mixed use enterprise SSDs: 3-5 DWPD
- Write-intensive enterprise SSDs: 5-10+ DWPD
For perspective, a DWPD rating of 1 equates to writing the full drive capacity once per day. So a 1 DWPD rating over a 5 year period would require writing the SSD’s full capacity 1825 times, or a total capacity write of around 1.8 Petabytes for a 1TB SSD.
Enterprise drives can achieve much higher write endurance through the use of SLC NAND flash instead of TLC. SLC NAND can reliably sustain 30-50+ DWPD making it ideal for extremely write-intensive applications like caching.
How is SSD Endurance Improving?
Although lower process NAND generally has incrementally lower endurance characteristics, SSD write endurance has continued improving over time through a combination of controller innovations and proprietary NAND advances from manufacturers.
For example, Samsung claims their 970 EVO Plus SSDs use upgraded 92-layer V-NAND flash that provides 2X the endurance of their previous 64-layer V-NAND while maintaining the same 0.3 DWPD rating. Meanwhile, Western Digital and others have introduced “pseudo-SLC” modes that can flexibly dedicate a portion of TLC NAND capacity to temporarily operating in high-endurance SLC mode.
As SSD adoption grows for both consumer and enterprise use cases, the drive to improve endurance while maintaining affordability and high storage density will continue. With upcoming storage technologies like QLC NAND and new architectures like Zoned Namespaces (ZNS), endurance and reliability will remain a key focus area for SSD engineering teams.
Estimating SSD Lifetime Based on Usage
The lifetime endurance rating assigned to an SSD provides a useful baseline. However, the actual usable lifespan of your SSD will depend heavily on your real-world usage and write traffic patterns.
Heavy sequential write workloads will approach closer to the drive’s maximum endurance rating, while lighter random write workloads with sufficient idle time for garbage collection will extend usable SSD lifetime.
An SSD’s lifespan also depends on write amplification – the amount of actual NAND writes required for each write operation from the host system. The more inflated write amplification is, the faster the drive will consume its rated endurance.
To estimate your real-world SSD endurance, you can monitor indicators like the lifetime writes attribute through SSD toolbox utilities. This tracks total TB written to estimate how much of the rated TBW capacity has been consumed.
You can also track wear indicators like percentage lifespan remaining or media wearout indicator if exposed by your SSD. When these reach low levels, it signals the SSD is nearing its write endurance limits.
Is SSD Wear Indicated by Performance?
SSD performance will generally remain steady throughout most of the SSD’s lifespan and not directly indicate wear or remaining endurance. However, as an SSD approaches the end of its usable life and write endurance limit, you may see more obvious degradation such as:
- Lower sequential write speeds and throughput
- More variable latency and reduced responsiveness during writes
- Higher frequency of uncorrectable errors on writes
The SSD controller will have a harder time finding available good blocks for writing data as an increasing percentage of NAND flash has become unreliable or damaged from excessive wear. This leads to the controller needing to do more background processing like garbage collection, reducing performance.
If you notice these types of performance changes, it likely indicates the SSD is very near complete wear-out. However, normal SSD slowdowns from heavy sustained workloads are not necessarily signs of wear unless persistent.
Wear Leveling and Other Endurance Technologies
SSD controllers employ a number of key technologies focused specifically on improving write endurance:
Wear leveling
This involves intelligently distributing writes across the entire pool of NAND flash pages in an even manner. This prevents “hot spots” of heavily worn blocks while less-used blocks go untouched. Sophisticated wear leveling maximizes utilization of the full endurance capacity.
Over-provisioning
SSDs reserve extra hidden NAND flash capacity that is invisible to the host. Typically 5-30% extra capacity. This over-provisioning allows the controller to more efficiently manage wear leveling, garbage collection, and relocation of data as needed.
TRIM and garbage collection
The TRIM command and garbage collection processing works by identifying blocks of SSD capacity that are no longer in use and erasing them. This ensures these pages are ready for reuse, improving write efficiency.
Data integrity checks
Features like ECC error correction protect data integrity as cells wear out. Additional data integrity checks like CRC protect against corrupted writes being committed to worn-out NAND.
Caching and buffered writes
Intelligently caching data in volatile memory and coalescing multiple writes into single larger program operations helps reduce unnecessary writes that would contribute to wear.
Does Erasing an SSD or Secure Erase Increase Endurance?
Erasing an SSD using the secure erase feature, or erase tools provided by SSD manufacturers, does not actually increase the drive’s write endurance. The total TBW rating for an SSD is fixed and based on the NAND it uses.
However, securely erasing your SSD will restore performance to like-new state. This is because a secure erase command initializes all cells to empty and allows the controller to rebuild optimal internal mappings and usage tracking.
Heavy sustained workloads that have caused significant wear leveling or garbage collection overhead can be cleared by a secure erase. This eliminates any inactive blocks and clears any ongoing background work, effectively letting the controller start fresh.
Increasing SSD Endurance – Key Takeaways
- The total TBW endurance rating for an SSD is fixed, based on the NAND it uses. Secure erase does not increase this number.
- Higher capacity SSDs have proportionally higher TBW endurance ratings.
- Enterprise SSDs support much higher write workloads than consumer SSDs through techniques like SLC NAND.
- Controller technologies like wear leveling, ECC, caching, and garbage collection are critical to maximizing real-world SSD endurance.
- Monitoring lifetime writes lets you gauge precisely how much of rated endurance remains.
| SSD Type | Average Endurance |
|---|---|
| Consumer/Client SSD | 300-600 TBW |
| Read-optimized Enterprise SSD | 1-3 DWPD |
| Mixed Use Enterprise SSD | 3-5 DWPD |
| Write-Intensive Enterprise SSD | 5-10+ DWPD |
Conclusion
SSD write endurance has improved steadily over generations thanks to advances in NAND flash and SSD controllers. While reduced process NAND generally has incrementally lower endurance, techniques like pseudo-SLC help compensate and continue driving higher SSD lifetimes.
For today’s SSDs, 300-600 TBW is a reasonable average write endurance figure for consumer drives. But high-end desktop and enterprise SSDs can still provide 1 PB or higher total writes under heavy workloads. Monitoring tools that track lifetime writes or wear indicators provide the most accuracy for estimating remaining SSD endurance.
Carefully choosing an SSD rated for your workload patterns and properly provisioning usable capacity is key. With quality drives from tier 1 brands, SSDs can still reliably serve most applications for many years even on the low end of the rated write endurance spectrum.