[RFC/PATCH 0/5 v2] mtd:ubi: Read disturb and Data retention handling

[Artem Bityutskiy]

On Thu, 2014-11-06 at 14:16 +0200, Tanya Brokhman wrote:
> > There is also the "radiation" effect. Say, you have 3 continuous
> PEBs A,
> > B, C. And some PEB D which is far away from them. You never change
> A, C,
> > and D, you only read them. And you change B many times. IIUC, the
> > radiation effect is that A and C will accumulate bit-flips earlier
> than
> > D, because D is being erased and re-programmed.
> 
> I think you got confused with the block-names (A B C D) because it 
> doesn't make sense :) You said D never changes, just read from.

A, C - read, written, erased relatively often.
B, D - only read with the same rate.

B will gain bit flips quicker than D due to the radiation effect. On
some NANDs like MLC a lot quicker.

Disclaimer: I am not a HW expert, this is my understanding.

The patches in question do not cover this "radiation" effect.

The "read all periodically and scrub if enough bit-flips" approach
covers the radiation effect, just like the other NAND effects
(read-disturb, aging).

Artem.