The original post: /r/datahoarder by /u/GermanPCBHacker on 2024-10-02 15:53:02.
We all know, that the cells of NAND discharge over time if not plugged in, leading to a loss of data. (Do we?) So far so good. But is this really that simple? Will plugging in the SD card, USB flash drive, SATA/PCIe SSD prevent this data loss effectively?
We all know, that writing data to a used cell first requires deleting (nulling) the cell. Okay, so with the logic of "Leaving it unpowered will lead to dataloss" we would not be fools to assume, that plugging in regularly or permanently on the other hand will retain the data. But that misses the point of the logic on how cells are written if I am not a complete fool. They are basically nulled and than given a very specific charge by applying an exactly defined voltage that no one except the manufacturer knows.
I am not sure, if it is possible to just constantly re-apply the same voltage, because I also would assume, that the applied voltage likely does not match the cells voltage - after all it is not a battery that is charged, but a somewhat isolated cell, that charges have to migrate through the surrounding insulation layer of the silicon substrate. So just giving it the same pulse again... Who knows how parasytic effects will effect the actuall charge state of the cell.
Furthermore I also doubt, that most, if not all firmwares even have a specific feature to constantly "repair" the state of cells, as charges slowly migrate through the insulation over time.
So is there any *real* documentation on wether such a "keep-alive" is happening or even exists on a hardware level? Not just opinion or single experiences, but actual evidence? I would absolutely love to know. For what its worth - if there was a nondestructive keep-alive, it would be adequate to just give an SSD 5V every 6 month for whatever time it takes for the firmware to complete a keep-alive cycle and we would be able to store data "forever "on SSDs, wouldn't we? (except for the case, where the firmware actively rewrites the cells and therfore needs to delete them first, which implies a lot of wear).
GO!