question: the performance of jffs2 on UBI

question: the performance of jffs2 on UBI

[falls huang]

Hello!

    I've a question :

The UBI and jffs2  both provide wear leveling. Will the repeated
wear-leveling reduce the performance of system ?


btw: I'm new to UBI , if it's a foolish problem , please pardon me .... :-)

-- 
Regards
Falls Huang

Re: question: the performance of jffs2 on UBI

[Artem B. Bityutskiy]

falls huang wrote:
> The UBI and jffs2  both provide wear leveling. Will the repeated
> wear-leveling reduce the performance of system ?
I guess jffs2 ought to be slower on UBI, but little. My *very* rough 
test on mtdram device showed that JFFS2 over UBI is about 5% slower. But 
more accurate testing should be done.

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

Re: question: the performance of jffs2 on UBI

[Artem B. Bityutskiy]

Artem B. Bityutskiy wrote:
> falls huang wrote:
> 
>> The UBI and jffs2  both provide wear leveling. Will the repeated
>> wear-leveling reduce the performance of system ?
> 
> I guess jffs2 ought to be slower on UBI, but little. My *very* rough 
> test on mtdram device showed that JFFS2 over UBI is about 5% slower. But 
> more accurate testing should be done.

And note: of course, JFFS2 was not designed for UBI, so it does not use 
UBI advantages. But still, it makes a lot of sense to use JFFS2 over UBI 
because in this case you have much freedom in partitioning your flash as 
you like.

I'm planning to return to JFFS3 research/development some day and design 
JFFS2 to work on top of UBI devices.

The alternative way to is to create a good block device layer over UBI, 
and then use conventional file systems (N.B. the mtdblock driver is 
*not* a good block device layer).

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

Re: question: the performance of jffs2 on UBI

[Josh Boyer]

On 7/27/06, Artem B. Bityutskiy <dedekind@yandex.ru> wrote:
> The alternative way to is to create a good block device layer over UBI,
> and then use conventional file systems (N.B. the mtdblock driver is
> *not* a good block device layer).

Just a note, you lose compression if you do that.  AFAIK, jffs2 is the
only in-kernel filesystem that supports transparent read/write
compression.

josh

Re: question: the performance of jffs2 on UBI

[Artem B. Bityutskiy]

Josh Boyer wrote:
> Just a note, you lose compression if you do that.  AFAIK, jffs2 is the
> only in-kernel filesystem that supports transparent read/write
> compression.
> 

Yeah, that's true. Although Reiser4 claims t osupport it. Nevertheless, 
I didn't try it.

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