ubifs: missing FAQ item regarding default compression options?

[Daniel Drake]

Hi,

OLPC is looking more seriously at making the switch from jffs2 to
ubifs. We did this for a few months but we found that ubifs has
significantly higher (10-15%) disk space requirements for the same
data, compared with jffs2. We switched back to jffs2 because of this,
promising to look at ubifs again later (i.e. now).

What I didn't realise clearly at the time is that mkfs.jffs2 defaults
to zlib compression, and mkfs.ubifs defaults to LZO compression. So,
this was not a fair test. If I switch ubifs to zlib compression, it
produces results very similar to jffs.

For example, for one OS image, mkfs.jffs2 + sumtool produced a 664mb
file. mkfs.ubifs (with zlib selected) + ubinize created a 668mb image
of the same data - very comparable.

Should this be a FAQ entry? Others who aren't aware of this difference
in default compression options may run into the same non-issue.

Thanks,
Daniel