optimum geometry

Jörn Engel joern at wohnheim.fh-wedel.de
Tue Jan 22 05:21:04 EST 2002


> >  I'm beginning to fear that this is far from optimum.  What is an
> > optimum erase block size?
> As small as possible. The free space required by JFFS2 is measured in 
> blocks. It could probably be reduced to 2 or 3 blocks from the current 5/6 
> but will always be a straight multiple of blocksize, I think.

I partially disagree. You are absolutely right about the "unused"
blocks. But with mkfs.jffs2, I create smaller images with a blocksize
of 128k, than with a blocksize of 64k. This makes sense, as jffs[12]
must store some information per eraseblock, so fewer eraseblocks mean
less overhead.
In effect, there is an optimal erase block size, depending on the size
of your filesystem, where the sum of both effects is minimal. But in
most currently practical cases, the smallest possible is still the


Remember that not getting what you want
is sometimes a wonderful stroke of luck.

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