[weinzierl]

I find this a super interesting question. I always assumed that long term stability of electronic non-volatile memory is worse than that of magnetic memory. When I think about it, I can't think of any compelling reason why that should be the case. Trapped electrons vs magnetic regions; I have no intuition which one of them is likely to be more stable.

There is a question on stackoverflow about this topic with many answers but no definitive conclusion. There seem to be some papers touching the subject but at a glance I couldn't find anything useful in them.

[1] https://superuser.com/questions/4307/what-lasts-longer-data-...

[olejorgenb]

According to https://www.ni.com/en-no/support/documentation/supplemental/... (Seems kinda reputable at least)

"The level of charge in each cell must be kept within certain thresholds to maintain data integrity. Unfortunately, charge leaks from flash cells over time, and if too much charge is lost then the data stored will also be lost.

During normal operation, the flash drive firmware routinely refreshes the cells to restore lost charge. However, when the flash is not powered the state of charge will naturally degrade with time. The rate of charge loss, and sensitivity of the flash to that loss, is impacted by the flash structure, amount of flash wear (number of P/E cycles performed on the cell), and the storage temperature. Flash Cell Endurance specifications usually assume a minimum data retention duration of 12 months at the end of drive life."

[wtallis]

> During normal operation, the flash drive firmware routinely refreshes the cells to restore lost charge. However, when the flash is not powered the state of charge will naturally degrade with time.

You have to be careful how you interpret this bit. "Normal operation" here assumes not just that the SSD is powered, but that it is actively used to perform IO. Writes to the SSD will eventually cause data to be refreshed as a consequence of wear leveling; if you write 1TB per month to a 1TB drive then every (in-use) cell will be refreshed approximately monthly, and data degradation won't be a problem.

If you have an extremely low-write workload, the natural turnover due to wear leveling won't keep the data particularly fresh and you'll be dependent on the SSD re-writing data when it notices (correctable) read errors, which means data that is never accessed could degrade without being caught. But in this scenario, you're writing so little to the drive that the flash stays more or less new, and should have quite long data retention even without refreshing stored data.

[dataflow]

> When I think about it, I can't think of any compelling reason why that should be the case. Trapped electrons vs magnetic regions; I have no intuition which one of them is likely to be more stable.

My layman intuition (which could be totally wrong) is that trapped electrons have a natural tendency to escape due to pure thermal jitter. Whereas magnetic materials tend to stick together, so there's at least that. Don't how much of this matches the actual electron physics/technology though...

[sharikone]

Hmm I don't think this is conclusive. Thermal jitter makes magnetic boundaries change too, and of course you have to add to it that it is more susceptible to magnetic interference.

I don't have intuition either, but I don't think this explanation is sufficient

[madacol]

> Trapped electrons vs magnetic regions;

From the physics point of view, aren't both cases the same thing?.

Isn't magnetic regions a state of the electric field? so if I move electrons in and out, the electric field should be changing as well

[mananaysiempre]

No. A region of a piece of material is magnetized in a certain direction when its (ionized) atoms are mostly oriented in that direction, the presence of a constant magnetic field is (roughly speaking) only a consequence of that.

So flash memory is about the electrons, while magnetic memory is about the ions.

[pas]

Aren't permanent magnetics a direct result of oriented spins? (So due to quantum effects?)