Does anyone know if a NAND flash device (e.g. microSD) has to be continuously supplied with energy for its wear leveling algorithms work as designed? Or, if it doesn't matter if the device is (safely) removed from the host, or if the host (safely) shuts down?

EDIT: I'm am sorry for the unclear question, what I've meant to ask was if the SD's microcontroller has any means to "remember" the history of writes and reads after a (safe) shutdown. I mean, I know the answer would be obvious if the algorithms relied on data stored on volatile memory, but I know it is safe to assume that no volatile memory is present on these drives. So my question is, if the data the wear-leveling algorithms rely on to perform as designed is present after a shutdown.

Again, I am so sorry for the confusion!

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    \$\begingroup\$ Wear leveling is just a means to distribute write operations so that a section of memory does not fail significantly prior to others. When it is not powered, it cannot be written to. \$\endgroup\$
    – JYelton
    Feb 13, 2020 at 22:24
  • \$\begingroup\$ Power can be cut off when the card is sitting idle. If there are no read or write operations that are pending, and the timings of the card are obeyed after writing and reading, it should be done with the wear leveling. Note that the wear leveling applies also to reading, as the data can be refreshed if reading it too many times makes it weaker. The phenomenon is called Read Disturb. \$\endgroup\$
    – Justme
    Feb 13, 2020 at 23:07

1 Answer 1


If you have safely removed the device from the host, then the wear level in algorithm is not doing any background task and it is already unmounted. You can remove power or shutdown the host.


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