AW: UBI bitrot checking and scrubbing

[Stelling Carsten]

Hi Richard,

> But you are right we should revive ubihealthd and the needed kernel
> interface because for Fastmap
> this is a topic.
I think it's a topic for all devices with or without Fastmap enabled, but rarely
powered off and on, or rebooted. For SLC NAND, data retention is specified
with 5 to 10 years, dependent on type and manufacturer. But data retention
time degrades with temperature and the number of P/E cycles. Read and write
disturbance is another influencing variable, which must be taken into account.
Therefore, it is only a matter of time, when accumulated bitflips within a page
cannot be corrected by the ECC. Most often, these accumulation of bitflips is
not detected while the device is operating, because executable code was read
from NAND, copied to RAM and executed there. But during reboot, e.g. caused
by power interruption, the executable code or other rootfs content cannot be
loaded properly, causing the system to fail.

> Would you volunteer to forward port the patches?
I'm stuck with a 3.14 kernel. If I've been given a timeslot to update the kernel
and toolchain, I would like to do the forward port. But actually, this seems not
possible for the next few month.

Thank you.
Carsten



______________________________________
 Carsten Stelling
F&E Hardware / R&D Hardware

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