Re: JFFS2 node versioning problem?

Dmitry Bazhenov
2006-05-03T15:07:16Z

On Wednesday 03 May 2006 18:40, Artem B. Bityutskiy wrote:
> I meant, whether it can happen with a real-life flash device taking into
> account it's limited lifetime. Bear in mind, each eraseblock has limited
> resource. I guess for huge flashes this may be the case, but JFFS2 is
> not usable on them anyway. I'm too lazy to look at digits.

I have made some estimates and agree, that lifetime of an ordinal flash device
is significantly less than the point where the maximum version value is
achieved. For example:
Partition size: 1MB
Erase block size: 128KB
Block count: 8
Average node len: 150b
Maximum erase count: 100 000
max_ver_per_blok = (Erase block size) / (Average node len) = 128KB / 150
= 874
max_ver_per_erase_cycle = (Block count) * max_ver_per_block = 8 * 874
= 6990
max_ver = (Maximum erase count) * max_ver_per_erase_cycle = 699 * 10^6
= 0x29AAAAAA

But, how about the guys who make image snapshots? I understand, that it is
better to copy all information to some place, format the partition and copy
the informatuib back. But, if someone would want to make an image snapshot of
a JFFS2 partition in order to restore it somewhen later. In this case version
numbers retain. And they can be big. However, maybe it is not worth talking
about it.

--
Regards,
Dmitry