Re: UBI Used In Commercial Products ??

[Jamie Lokier <jamie@shareable.org>]

Sergei Sharonov wrote:
> 2 hours of mount time after I used ftp to transfer large file.

Wow!

> I really hope UBI+UBIFS will overcome this problem. Still there is a
> concern here since UBI scales linearly. Can somebody plz post UBI
> scan time for large flash array?

The only way to get sub-linear scaling is to designate a sub-linear
subset of eraseblocks which are read at scanning/mount time.

Doing that at the same time as wearing all eraseblocks equally is
quite tricky, and probably requires a phase tree and multi-headed
logging structure, like LogFS (I'm not sure if LogFS actually does
both, though).

Such a structure is not particularly simple, and will be present in
the best flash filesystems eventually.  So I wonder if UBI is really a
good place to have a second copy of those algorithms.

I like the idea of UBI, to abstract block allocation and wear tracking
from the filesystem, but it seems the sub-linear scan time requirement
is a tricky one to do without implementing a non-trivial
filesystem-like algorithm in UBI itself.

I'll be delighted to read that the problem's been solved, when it has
been solved, though :-)

-- Jamie