How do computers keep time

This is how long data will last on SSDs without a power supply

Friedrich Stiemer

On the Internet, one repeatedly comes across the question of whether SSDs can lose data if they have been disconnected from the power supply for a long time. What's up

EnlargeThis is how long data on SSDs without a power supply last

One faction swears by SSDs, considers them reliable and is absolutely convinced of the technology. The other group is skeptical as to whether an SSD can do at least as much or even more than a conventional hard drive with rotating magnetic disks. Now a rumor is spreading about SSDs on the Internet, which has made critics even more doubtful - triggered by the question of whether a flash memory can lose data if it has been disconnected from the power supply for a long period of time.

One answer to this can be found using the example of the boot process of your PC: The computer fetches the operating system from the hard disk and writes it to the main memory (RAM). This process happens every time the computer is switched on, since the RAM can only write data with a power supply. Now an SSD works with memory chips that are very similar to the main memory, which is why one could assume that the SSDs also need a constant power supply in order to save files. However, this is not the case. Rather, flash memories use so-called NAND flash chips, which have a different type of gateway wiring. It ensures that a certain power supply is maintained even when the system is switched off. In addition, the flash memory has a special property called a “floating gate”. This is electrical insulation that prevents external influences. Thanks to these protective measures, it can definitely be said that an SSD is suitable long-term storage.

EnlargeAn SSD is not unlike a RAM, but unlike RAM, it retains the data even when the power supply is cut - but not forever.

At the same time, the ambient temperature of the storage medium has an impact on the service life of the data when the power supply is cut. If the temperature at the storage location is constant at 25 degrees Celsius, the data will be stored in the memory for around two years. However, if it increases by five degrees, then the life span is already halved. However, these figures are very theoretical. Because the actual time until data loss differs from model to model, as structural differences also play a role in production. Basically, however, you should not store an SSD in a warm, but not too hot environment for longer than two years without power, in order not to endanger your data stored on it.

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