"Remaining user data" on a JFFS2 image/partition

"Remaining user data" on a JFFS2 image/partition

[Bernhard Priewasser]

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Hello,

I just ran some tests on JFFS2 "space consumption" (note: total image 
size is limited due to mtdram). You can see the portion of disk space 
used for "management" information of JFFS2 depending on erase block size 
and total image size in overhead_total_size.emf (axis "Non-User-Data 
Proportion" showing percentage); the results are as expected.

overhead_scaling.emf shows absolute "overhead" space consumption in 
kilobytes depending on total image size.
-> Conclusions/Questions:

1) JFFS2 needs at least total_size = 4*erase_size to mount (wow...)

2) While total_size <= 32*erase_size JFFS2 "overhead" does NOT vary.
    Why?

3) Overhead seems to roughly depend linear on total size. (wow...)
    But: Why only rouhgly? (Varying gradients at total_size >
    32*erase_size)

4) Out of 2) and 3): On what internal structures (number, size, ...)
    does the "overhead" exactly depend? jffs2_eraseblock, ...

Regards & Thanks,
Bernhard

PS: All preliminary.

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