SanDisk 400GB microSD card!

Jun 7, 2008
101
4
How many guaranteed write operations per cell?
Sandisk doesn't specify. (Ultra microSD UHS-I CARD | SanDisk) The answer would depend on exactly what sort of NAND Flash was used.

But I think the question you're asking is "How many times a cell can be written to before it becomes unusable?"

The answer for the sort of flash used these days is "about 10,000" And the drive firmware attempts to distribute writes evenly across the drive. So the bigger question is "How long will it take for any individual cell to to be wriiten to 10,000 times?" The answer for normal usage is that you'll be replacing the drive with something larger/faster long before you notice drive ware.
 
Jun 7, 2008
101
4
Do realize that SD card does not have "drive firmware".
I realize no such thing, because they do have "drive firmware"

SD cards are removable drives, and all current drives have onboard controllers and firmware.

In the case of SD cards, the controller is usually a modified 8051 CPU or an ARM variant.

See On MicroSD Problems « bunnie's blog for some interesting hacking of SD cards and onboard controllers.

And the firmware on SD cards attempts to do wear leveling, so my comments about number of times a call can be written to and overall drive life stand.