Re: JFFS2 node versioning problem?

[Dmitry Bazhenov <atrey@emcraft.com>]

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