The problem that I didn't think out

Artem B. Bityutskiy dedekind at yandex.ru
Sun Nov 27 08:20:19 EST 2005


Ferenc, Greetings!

> We had some time, so we read the plan of JFFS3 (with RaiserFS
> documentation).
Oh, what a delightful news! :-)

> The key compression is the only one in the plan that I think that is
> better if we don't use. I think to make key management as simple and
> fast as possible is more important than some percent in flash usage. (if
> I am right the bottleneck of real products is not the flash usage but
> the speed) But it is small techniqual question.
Well, I would not agree, compression Guru Ferenc though you be :-) When 
you start thinking about GC, you'll notice that Indexing nodes are to be 
rewritten *a great deal* of times. So, the smaller is the index, the 
faster is JFFS3. The main idea of key compression is *not* to save flash 
space, but to lessen the (index size)/(data size) ratio.

Nonetheless, tests should show the worthiness of keys compression. There 
is obviously a (CPU time) vs. (amount of flash IO) trade-off. Thus, I 
offer to wait for a JFFS3 prototype and evaluate this. Let's mark this 
stuff as "to be evaluated".

> The big questions are that questions you already thinging on: garbage
> collection and wear leveling. Without solving them JFFS3 have no nice
> future. I only would like to say that now we are also thinking on these
> important problems... and we will write if anything usable found. (I may
> be better feeling to thinking on someting not alone... :) )
Great! :-)

Thank you for this feedback.

-- 
Best Regards,
Artem B. Bityutskiy,
St.-Petersburg, Russia.




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