Re: How Do SSDs Wear Out?

On 2025-02-14 09:11, Paul wrote:
> On Fri, 2/14/2025 12:47 AM, Boris wrote:

...

> The physical cells, the structure at the atomic level, is
> damaged by the writes.
> 
> Each cell has a "voltage" stored on it. Established by putting
> some electrons on a floating gate. The path for this is
> quantum mechanically disallowed, and to get the electrons
> onto the gate requires tunneling. The electrons will sit
> on the gate for up to ten years (retention time estimate, info
> on this has not been updated in a long long time so we are left
> to guess whether it scales in any way with gate size).

I wonder if we can store the disk for five years, then plug it in and 
somehow refresh the charges in the cells.

...

> By mapping the sectors, using a mapping table, and "moving the MBR around
> each time it is written", that is wear leveling. The drive has a pool of
> unwritten blocks. On a write request, an unused block is written.
> Perhaps the block is at address 27, and it contained MBR sector 0.
> The map file the drive keeps then, it has to remember that aspect.
> On a read, we request sector 0, the map goes "oh, that is block 27",
> and the drive does the read at that address, and there is our MBR.
> Now, if I abuse the MBR by writing it a lot, a hole isn't burned in it.
> The sector has been "virtualized", and only the mapping table knows
> where my sector is stored :-)

Where is the map stored? I always wondered about this.

...


Thanks a lot for the summary :-)


-- 
Cheers, Carlos.