ext2 for read-only file system on UBI

[Hamish Moffatt]

Hi Artem, thanks for your response.

On Mon, May 19, 2008 at 09:37:53AM +0300, Artem Bityutskiy wrote:
> On Mon, 2008-05-19 at 16:21 +1000, Hamish Moffatt wrote:
> > My embedded device has a read-only root file system which is only
> > replaced by writing a whole image (dd, flashcp, ubiupdatevol etc).
> > 
> > Using gluebi and mtdblock, I think I can put a traditional block file
> > system (eg ext2) on top of NAND flash. What are the disadvantages of
> > this? (For the read-only application only.)
> 
> For read-only it should be ok, although I am not sure mtdblock will like
> non power of 2 eraseblock sizes. But this should be trivial to fix.
> 
> > Background: I've got older hardware which uses ext2 on top of compact
> > flash in IDE mode, and new hardware which has replaced the compact flash
> > with NAND. I'd like to share an ext2 image between the two if possible.
> 
> Should be possible for R/O. Different sizes of eraseblocks may add extra
> work though.
> 
> > The read-write file systems use ubifs. I'm only considering this for the
> > read-only volumes. One obvious disadvantage is lack of compression. Are
> > there others? Do I still get the reliability of ubi? 
> 
> No, should be fine. Well, you'll still have WL across whole NAND chip,
> yes. You'll still have bit-flip handling.

So, is there a benefit to Nancy's proposed ubi block layer as opposed to
gluebi + mtdblock?
( http://lists.infradead.org/pipermail/linux-mtd/2008-May/021609.html )

regards
Hamish
-- 
Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>