fast-mounting read-only file system on NAND flash / UBI experience ?

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Hello all,

I'm looking into options for a file system to use on a 32MB NAND
flash. JFFS2 as it currently stands has to go away, as the mounting
takes over 12 seconds on this small ARM system, which is getting
increasingly unacceptable. On the other hand, a read-only file system
(combined with a small tmpfs RAM disk) is no problem.

cramfs works very nicely on the /dev/mtdblockX device and does all I
want. But of course cramfs is usable only as long as the NAND has no
bad blocks since cramfs itself is not flash-aware. Throwing away the
hardware whenever there's a block error would generate unacceptable
levels of waste and repair costs in this project.

I'm currently still using a patched kernel (with updated MTD/
JFFS2 and a bunch of in-house patches) but switching to a newer one is
not ruled out.

The file system is currently being written to NAND by U-BOOT.

Currently I see the following options:

1.) Using some kind of patched, flash-aware crams / squashfs / romfs
or similar, if it exists. Does it?

2.) Running cramfs or another read-only fs on top of UBI (either by
switching kernels or by patching UBI into my current kernel).

3.) Using some kind of general-purpose Flash Translation Layer, if one
exists that will mount decidedly faster than JFFS2.

I'd like to ask:

1.) if anybody around here has solved this sort of problem in some
kind of satisfactory way.

2.) if anybody has had either good or bad experiences with UBI. One
very important question would be, is the mount time for UBI really
lower than for JFFS2?

3.) if UBI works together in some sort of usable way with U-BOOT.
Especially, is there a reasonably simple way to make UBI images and
write them to flash with U-BOOT.

Thanks for any help!

Linards Ticmanis

Re: fast-mounting read-only file system on NAND flash / UBI experience ?

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Have you looked at YAFFS ? (try Google). Unlike JFFS2 it was designed
from the ground up to support NAND. Support exists to mount images from

Re: fast-mounting read-only file system on NAND flash / UBI experience ?
On 26 Jun., 22:51, "Geronimo W. Christ Esq"

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Thanks for the hint, I have looked at it now.

Unfortunately our design cannot guarantee clean shutdown, most
shutdowns will simply be power-off - with no chance to react. It looks
like YAFFS is just as slow as JFFS2 when mounting a file system that
hasn't been shut down properly.

If you or anybody else has an idea for a better place to put my
questions, I'd be glad to hear about that as well.


Linards Ticmanis

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