The Flash Memory cells used in SSDs have limited P/E (Program/Erase) Cycles. Each time the data is written to an SSD memory cell, it degrades it slightly. So, a cell can be written a limited number of times. Once these P/E cycles have been reached, your SSD will no longer be reliable for data storage. But, how long does a drive last under different types of loads? We will discuss this topic in the article.
As we all know, SSDs store data in the form of an electric charge inside a floating gate or Charge-Trap memory cell. Depending on the type of NAND flash, the cell can store one, two, three, or four bits of data. In the consumer SSD market, there are two main options:Â TLC and QLCÂ NAND flash. TLC has a higher life expectancy inherited from its design and working principle. At the same time, QLC is considered the worst type of NAND flash memory in terms of both performance and reliability.
Each SSD comes with its TBW (Terabytes Written), which is one of the few parameters we can use to estimate the remaining life of an SSD. Within the warranty period of an SSD, this TBW number can be considered a benchmark of how much data can be written to our drive. These numbers are generally huge and are hardly surpassed by an average user. However, this can indicate how resilient your SSD is. However, to provide some numbers, we’ll need to examine studies, as there are many types of SSDs with different configurations. There are numerous brands with their own manufacturing methods. So, it isn’t easy for anyone to tell you the absolute SSD life expectancy.
However, the life expectancy of an SSD typically ranges from 5 to 10 years, depending on several factors, including usage patterns, technology, and drive type. Keep in mind that these aren’t absolute numbers, and there are several caveats to consider. Let’s discuss.
Factors Deciding SSD’s Life Expectancy
The 4 main factors that determine an SSD’s life expectancy are.
1. NAND Flash Type
Different NAND flash types have different P/E cycles. SLC has the best endurance, high P/E cycles, and fastest performance. QLC has the lowest endurance and the lowest P/E cycle. MLC and TLC NAND flash come between these two. Here is the table showing the estimated P/E cycles of different NAND flash types.
| NAND Type | P/E Cycle Endurance (Typical Range) |
|---|---|
| SLC (Single-Level Cell) | 90,000 – 100,000 cycles |
| MLC (Multi-Level Cell) | 3,000 – 10,000 cycles |
| TLC (Triple-Level Cell) | 1,000 – 5,000 cycles |
| QLC (Quad-Level Cell) | 100 – 1,000 cycles |
| PLC (Penta-Level Cell) | < 100 cycles (expected) |
A lower P/E cycle of a NAND flash memory indicates lower endurance and hence lower life expectancy. In the consumer market, you have the option to choose between the TLC and QLC. So, if you decide TLC, you are actually selecting a drive with a better life expectancy.
2. TBW (Terabytes Written)
NAND Flash type is one thing. But manufacturers also rate their SSDs for different TBW (Terabytes Written) numbers. Two different SSDs with the same type of NAND flash memory can have different TBW ratings. TBW is an indicator of the total amount of data that can be written to the SSD over its lifetime before it begins to degrade. Higher TBW means an SSD with a longer life. From the TBW, you can easily determine the DWPD (Drive Writes Per Day), which is another measure derived from the TBW. It indicates how many times the entire capacity of an SSD can be written per day over its warranty period.
3. Usage and Operating Environment
Now, this is under the control of the user on how they use their drive. Any drive being used at high ambient temperatures will degrade faster, and the change of charge leakage will increase. Not only the temperature but also humidity and physical shocks can have an impact on an SSD’s life expectancy. Along with that, if you use your SSD intensively, it can eventually reach its TBW limit and the P/E cycle numbers. This is rare, but still, SSDs have a limited lifespan, and it can be accelerated with heavy usage.
4. Wear-Leveling Algorithm
Without the wear-leveling algorithm, an SSD would store incoming data in the first available empty block or repeatedly write to the same blocks that are easily accessible. This might be beneficial for the performance, but some cells would wear out faster because they are not being utilized evenly. With the wear-leveling algorithms, the damage (during writing) to the cells is evenly distributed across the memory layers. This ensures that no cell is undergoing overuse while others remain idle. This might sound simple, but it has a pretty big role in increasing SSD’s life expectancy.
There are also other factors, such as over-provisioning, DRAM, TRIM, ECC, and Bad block management, that work together to ensure the NAND flash cells are utilized as efficiently as possible. DRAM contributes not only to maintaining the FTL but also to storing the frequency read/written data, thereby reducing the number of writes to the memory cells. ECC ensures that the data is properly stored and in good condition for reading. Over-provisioning is the extra space set aside by the SSD for wear-leveling, garbage collection, and bad block management algorithms. The TRIM command informs the SSD which data blocks are no longer required and are ready to be erased. This helps increase performance and reduce unnecessary write operations.
All in all, numerous factors contribute to the overall life expectancy of an SSD. A well-designed and manufactured SSD will always ensure that it employs all these features. However, how we use our SSDs also plays a significant role in determining their lifespan.
What do the studies say?
This topic is moot if we don’t discuss Backblaze’s ongoing SSD initiative, where they have employed thousands of SSDs from various brands. So far, the SSDs have maintained an Annualized Failure Rate (AFR) of 1% or less through the first four years, according to Backblaze.
This popular study concludes that the overall AFR for all SSDs in the dataset is 1.16%. In this, the AFR of MLC SSDS ranges from 0.16% to 2.52%, and 3D-TLC SSDs exceed 3%. A lower AFR suggests better reliability and potentially longer life expectancy for those drives.
An old study done by Facebook concludes that write-intensive applications affect SSD longevity. They used different workloads for reading and writing data. They found that write-intensive applications led to a higher incidence of intra-node and intra-rack failures compared to read-heavy applications.
Unfortunately, there are no direct studies that tell us the SSD life expectancy by testing many SSDs under a controlled environment. There are studies for enterprise drives like the Google and Facebook research that we discussed earlier. However, it is challenging to conduct any study on consumer SSDs. Backblaze’s ongoing study is a good way to know the performance of some SSDs that they have been testing. However, they can’t test all the SSDs out there. Therefore, it is best to know your SSD’s specs, such as TBW and MTBF, before purchasing it.
What should you expect from your SSD?
Any consumer-grade SSDs would easily last 5 to 10 years under low to medium workloads. In heavy workloads, you may see your SSD going bad before 5 years as well. However, you don’t have to worry too much if you have picked a good brand, a TLC SSD with DRAM, and good TBW, along with a moderate temperature for your SSD. However, it is better to have a backup of your system in case of a serious drive failure.
So, how long do SSDs last?
Most SSD manufacturers claim 5–10 years of operational life under normal usage conditions. Regarding the failures, A Google+ + University of Toronto study found that age is a better indicator of SSD age than write volume.
Therefore, it is clear that there is no definitive number to determine your SSD’s life expectancy. It is best to follow best practices to extend your SSD’s lifespan and maintain regular backups of important data. Also, it is better not to use your SSD for critical data storage after its warranty period or when the TBW is exhausted.
I hope this helps!
