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 a little bit. So, a cell can be written a limited number of times. Once, these P/E cycles have reached, your SSD remains no more reliable for data storage. But, how long does a drive last under different types of loads? We will discuss that in this article.
As we all know, SSDs store data in the form of 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, we have two main options i.e. TLC and QLC NAND flash. TLC has got higher life expectancy inherited by its design and working principle. However, 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 check to estimate the remaining life of an SSD. Within the warranty period of an SSD, this TBW number can be considered as a benchmark of how much data can we write on our drive. These numbers are generally huge and are hardly surpassed by an average user. But, this can tell how resilient your SSD is. But, to tell you some numbers, we’ll have to look at some studies because there are many types of SSDs with different configurations. There are a lot of brands with their manufacturing methods. So, it isn’t easy for anyone to tell you the absolute SSD life expectancy.
But, generally, an SSD’s life expectancy typically ranges from 5 to 10 years, depending on several factors, including usage patterns, technology, and drive type. However, these aren’t absolute numbers and there are a lot of caveats to it. Let’s discuss.
Factors Deciding SSD’s Life Expectancy
4 main factors are deciding an SSD’s life expectancy. Let’s discuss all of them one by one. Also, discuss some other things that are helpful in increasing SSD’s life expectancy.
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 lowest P/E cycle. MLC and TLC NAND flash come in between these both. 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 options to choose between the TLC and QLC. So, if you are choosing TLC, you are actually choosing a drive with 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 simply means an SSD with a longer life. From the TBW, you can easily get the DWPD (Drive Writes Per Day) which is another measure coming 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 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 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 limited and the P/E cycle numbers. This is rare but still, SSDs have limited amount of time for which they live and it can be fast-forwarded 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 makes sure that any cell isn’t undergoing overuse while others are sitting idle. This might sound simple but have a pretty big role in increasing SSD’s life expectancy.
There are some other things like over-provisioning, DRAM, TRIM, ECC, and Bad block management that work together to make sure the NAND flash cells are being utilized as efficiently as possible. DRAM contributes not only to maintaining the FTL but also to storing the frequency read/written data to reduce the number of writes on the memory cells. ECC is good to ensure the data is properly stored and is in good health when it comes to reading it. Over-provisioning is simply 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 block is no longer required and is ready to erase. This helps in increasing performance and reducing unnecessary write operations.
All in all, there are numerous things that contribute to the overall life expectancy of an SSD. A well-designed and manufactured SSD will always make sure to employ all these things. However, how we use our SSDs also plays a very important role in increasing or decreasing its lifespan.
What do the studies say?
This topic is nothing if we don’t discuss the backblaze’s ongoing SSD where they have employed thousands of SSDs from many brands. So far the SSDs have maintained a 1% or less Annualized Failure Rate (AFR) 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 aren’t any direct studies telling us the SSD life expectancy by testing many SSDs under a controlled environment. There are studies for enterprise drives like the Google and Facebook researches that we discussed earlier. But, it is hard to perform 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. So, it is best to know your SSD specs like TBW, MTBF, etc before you buy 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 any serious failure of your drive.
Importance of SSD Backups in critical environments
Backups are really important if your data is important to you. Any storage drive whether SSD or HDD can fail anytime because it is an electronic device at the end of the day. Also, you can’t suspect the upcoming failure early on. Nor you can repair your drive on your own. So, backups are really important even on personal computers.
I hope this helps!