SSD data retention is one of the most talked about topics in the storage community. This is because neither the manufacturer nor the user knows how long will an SSD last. The more specific question is how long an SSD will hold its data when we disconnect it from our computer. This question is asked mostly by the people who know the basics of SSDs. They know that the data is stored in the form of electric charge which leaks out from memory cells over time. The main argument is that if we don’t power an SSD for a very long time, say a year or two, will the SSD lose all its charge and wipe out all the data?
As per the JEDEC standards for consumer SSDs, SSDs after reaching their endurance limits, should be able to store the data for at least 1 year at 30°C. For enterprise SSDs, the retention period is at least 3 months at 40°C.
However, nobody exactly knows how long an SSD will keep its data in place once we disconnect it from the host system. However, there are different studies and standards set for the manufacturers which we are going to discuss in this article.
For consumer-grade SSDs, data retention typically ranges between 1 to 5 years without power under normal storage conditions i.e. around 30°C. Some manufacturers claim data retention of up to 10 years, but this can be shorter if the SSD is subjected to higher temperatures or if it has been heavily used during its lifespan. At room temperature (about 25°C), retention of up to 1 year is considered reliable, but at higher temperatures (30°C or more), data may only last a year or less.
No Specific Studies on SSD Data Retention without Power
Most of the articles on the internet tell you the general numbers and periods of data retention mostly from the JEDEC standards. Unfortunately, there aren’t any specific studies where the SSDs have been placed idle without power and then checked for the accuracy and the overall retention of the stored data. However, there are some common numbers which we can consider for our benefit. However, you can’t trust them blindly and put any sensitive data under the threat of permanent loss. Some studies have discussed different time frames for data retention which I will highlight in the upcoming section. But, there isn’t any specific study on this topic.
JEDEC SSD Standards for Data Retention
According to the latest JEDEC specifications for SSDs released in 2020 (JESD218C), a consumer SSD must retain the data for 1 year at 30°C.
According to this paper, a consumer SSD stored at 40°C will retain data for around 1 year. However, at 55°C, the retention period drops significantly to just weeks. However, these are just numbers specified by the JEDEC for the manufacturers. The real data retention period without power will depend heavily on your drive’s condition. Also, these numbers are for the drives that have written almost to their endurance ratings.
Talking about the charge leakage
The smallest memory unit in an SSD is a transistor. It could either be a Floating Gate transistor or its advanced version called Charge Trap Flash. The data is stored bit by bit in the form of an electric charge. A single cell can hold multiple bits of data. Inside the SSDs using the floating gate technology, the charge is stored in a conducting layer which is then insulated by a dielectric material. This layer is between the gate and the body of the transistor. In the charge trap flash, everything remains the same except the floating gate is replaced by a non-conductive material. This material is much better at holding the charge by storing it in discrete locations instead of a single material.
However, whatever the material and the storage technology utilized, NAND flash memory is prone to data loss due to this charge leakage. The amount and speed of this leakage would determine an SSD’s data retention capabilities. If the SSD has aged, the insulating material around the gate would allow the pass to leak easily. However, a new SSD will hold the data much more effectively. Read more about how SSDs store data without power.
What decides an SSD’s data retention capabilities without power?
1. NAND Flash Type
As we discussed earlier, the type of floating gate material used i.e. Floating Gate (2D) or Charge Trap (3D NAND) would determine an SSD’s data retention capabilities. However, the number of bits stored per cell would also have a great impact on data retention. SLC SSDs have the best data retention capabilities. After that comes, MLC, and then TLC followed by QLC with the lowest retention capabilities. You can read more about it in this study. With the increasing number of bits stored per cell, the data integrity reduces because of the multiple levels of discrete voltage levels.
SLC typically retains the data for up to 10 years without power under normal conditions.
2. Age of SSD and usage
If the SSD is used for a long period before you keep it idle without power, its data retention capabilities will be way less than a new SSD. If you have done excessive write operations on your drive, it may degrade the memory cells in a much harsh manner. This impacts a cell’s ability to keep the charge in its place. The data retention, in this case, will be reduced much more in the case of the floating gate cells. The charge trap layer can hold the data much more effectively compared to the floating gate even if the cells have degraded by heavy usage.
The reason a cell loses its ability to hold the charge after heavy usage is inherited in its design. To keep the charge stored inside the floating gate or charge trap, an insulation layer is provided around it. However, when the controller writes a bit or bits on this cell, it has to bypass this insulation layer. Every time the charge passes this layer, it degrades or wears it a little bit. So, the number of total write operations or P/E cycles will have a significant role in how effectively an SSD will retain its data without power.
3. Temperature
The charge inside a NAND flash memory cell can stay in place if the temperature is generally between 0 to 30°C. With higher temperatures than this, the charge can excite because of the external heat component. This would reduce an SSD’s data retention capability a lot. Studies suggest that for every 10°C increase in temperature, the retention time of NAND cells can roughly halve. However, no manufacturer will guarantee such exact numbers because it depends on factors like wear level, write cycles, SSD design, etc.
According to the same JEDEC guidelines we discussed above, the ideal temperature for the highest data retention in consumer SSDs is around 25°C. An SSD can hold data for 105 weeks at this temperature. According to this study on SSD data retention in 3D NAND Flash memory, an observation was that for every 10°C increase in temperature, the retention time can decrease by a factor of 2.
4. Manufacturing Quality
If the SSD is manufactured with poor quality control and cheap material, it will normally have bad data retention capabilities.
5. Controller and Error Correction
The controller and ECC algorithms may not have any direct impact on data retention when the SSD has no input power, but they have a major role in how the data is stored in each cell. Before an SSD is powered off, the controller and ECC work to ensure that data is correctly written, stored, and can be read without errors.
How long is the data retained without power?
The consumer SSDs mostly come with TLC and QLC NAND flash and this drive can hold the data for between 1 to 3 years without power. We imagine that the drive is still new to reach this conclusion. Because it varies depending on your SSD age, cell type, temperature, and manufacturing, you can just predict it. Let’s discuss what you can expect from what type of SSD.
SSD data retention (without power) based on cell type
As we all know now, SLC Flash memory has the best data retention capabilities because there is one possible voltage state in each cell i.e. high or low. So, even if some charge leaks out from a charged cell, the controller can easily detect the error when we plug our SSD back. The QLC has the lowest data retention as you can predict. However, these numbers will vary depending on SSD’s age and many other factors.
| NAND Cell Type | Data Retention (without power) | Endurance (P/E Cycles) |
|---|---|---|
| SLC (Single-Level Cell) | 10+ years | 100,000+ |
| MLC (Multi-Level Cell) | 3-5 years | 3,000 – 10,000 |
| TLC (Triple-Level Cell) | 1-3 years | 1,000 – 3,000 |
| QLC (Quad-Level Cell) | 1 year or less | 100 – 1,000 |
SSD Data Retention and Usage (Wear Level)
The data retention period that we discussed above is generally for the SSDs with low wear. So, even if your SSD is an MLC, but has surpassed 50% of its P/E cycles, its data retention capabilities will be reduced to more than half of the original. This will happen for all kinds of SSDs. However, if your SSD is TLC and QLC, and its wear has reached near the end limits, you should not use it to store any important data without power. Some worn-out SSD can even start to lose their data just within a week.
| Usage Condition (Wear Level) | Data Retention (Years) |
|---|---|
| New/Light Usage (Low Wear) | 5-10+ |
| Moderate Wear (50% life used) | 1-3 |
| High Wear (Near End-of-Life) | <1 |
According to this study again, the reduction in retention is more severe in TLC NAND after just 20-30% of the rated P/E cycles.
SSD Data Retention Variations in 2D vs 3D NAND Flash
| NAND Type | Data Retention Time (Without Power) | Factors Influencing Retention |
|---|---|---|
| 3D NAND | 5 – 10 years (for MLC/TLC), 10+ years (for SLC) | – Charge Trap Cell architecture reduces charge leakage – Higher endurance improves retention – ECC effectiveness |
| 2D NAND | 1 – 5 years (for TLC/QLC), up to 10 years (for SLC) | – Planar structure is more prone to charge loss – Limited scalability affects retention |
The 3D NAND flash with charge trap flash (which is most common these days) has better data retention capabilities as compared to the older 2D floating gate transistor technology. Because of the higher endurance of each cell and its ability to absorb the charge in discrete locations, these SSDs end up keeping the charge for long periods without power. Samsung has its marketing name for 3D flash called V-NAND which also has better retention capabilities compared to the 2D planar NAND flash.
How to increase the data retention period?
In the consumer SSD market, you have two options to choose for the cell type i.e. TLC and QLC. TLC generally has better data retention capabilities than QLC NAND Flash. Make sure to choose the SSD with charge-trap (3D) flash technology instead of the floating gate (2D). Then comes a good controller and DRAM. Also, an SSD with high TBW will have good endurance in the power-off state as well.
However, the storage temperature of your SSD is the most important thing here. Make sure to keep your SSD at a temperature below 40°C. Choose SSDs with ECC. Also, the best way according to me is to refresh the SSD by connecting it occasionally to your computer. You can also run the TRIM command to make sure everything is properly optimized. You can then unplug the drive again.
If you are planning to use an SSD for long-term data storage, it is good to pick a new SSD rather than an old and used one.
Which is best for long-term data storage: HDD or SSD?
Hard Drives are considered better than SSDs for long-term or cold data storage. Because the data is stored on magnetic platters in the form of magnetic fields, it is less prone to decay as compared to the electric charge in SSDs.
According to this study, SSDs typically have a data retention period of about 3-5 years when powered off, largely depending on the type of NAND flash used. The hard drives, on the other hand, can retain the data for 10 years or more under optimal conditions, assuming they are kept in a stable environment.
Another study says the same thing for HDDs with less data retention period for SSDs i.e. 1-2 years.
Hard drives can retain the data in a better way when powered off because magnetic storage is less susceptible to environmental noises as compared to charge-based storage systems. Also, the materials used in magnetic drives (typically ferromagnetic materials) are highly stable chemically. On the other hand, the semiconductors used in solid-state drives have the inherited property of charge leakage over time.
Both SSDs and HDD employ ECC which is effective in long-term storage but the hard drives can retain the data for longer because of its different operational principles.
However, this doesn’t mean you can’t use an SSD for long-term storage. Modern SSDs can keep the data for years without degradation provided that the drive is new and you have kept it in a cool environment (normally at 30 to 40°C). But, overall, Hard Drives have better theoretical data retention capabilities without power.