This is a very important property of SSDs and is a large reason why log structured storage is so popular in recent times. The SSD is very fast at appends, but changing data is much slower.
No, it's worse than that. The fact that it's an overly subtle distinction is the problem.
SSDs are fast while write traffic is light. From an operational standpoint, the drive is lying to you about its performance. Unless you are routinely stress testing your system to failure, you may have a very inaccurate picture of how your system performs under load, meaning you have done your capacity planning incorrectly, and you will be caught out with a production issue.
Ultimately it's the same sentiment as people who don't like the worst-case VACUUM behavior of Postgres - best-effort algorithms in your system of record make some people very cranky. They'd rather have higher latency with a smaller error range, because at least they can see the problem.
(Also you need the translation layer even for write-once since flash generally doesn't come 100% defect free. Not sure if manufacturers could try to get it there, but that'd probably drive the cost up massively. And the translation layer is there for rewritable flash anyway... the cost/benefit tradeoff is in favor of just living with a few bugged cells.)
FWIW, there are WORM microsd cards available but it looks like they still use flash under the hood.
Because of the Internet age there probably is not much place for write once media anyway, even it would be somewhat cheaper. But maybe for specialized applications or if it would be much much cheaper per GB.
Because the older Flash aren't as stable when miniaturized as you'd expect. Current flash is a direct descendant of these, they only are more stable because the cells are much chunkier and thus with lower leakage.
That being said, it's not clear how innovation has occurred in this direction in the storage space.
It could theoretically make them cheaper. But I guess that there wouldn't be enough demand, so you'd be better off having some kind of OS enforced limitation on it.
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-...
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...
I don't have intuition either, but I don't think this explanation is sufficient
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
So flash memory is about the electrons, while magnetic memory is about the ions.
"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."
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.
I mean... This is general purpose HW here. Write once SSD is a workflow more than an economically tenable use-case in terms of making massive size write once then burn the write circuit devices.