[U-Boot] understanding mkimage a bit more

[Eric Cooper <ecc@cmu.edu>]

On Fri, May 06, 2011 at 11:13:39AM -0700, Charles Krinke wrote:
> The next issue is the flash file system. Normally, I like to use JFFS2
> for reliability as embedded devices frequently have their power switch
> turned off at any time. I do understand that UBIFS is getting more
> prevalent lately and I wonder if you or anyone else has a comment on
> the suitability of UBIFS in an environment where the power will be
> turned off and on exexpectdly and frequently.
> 
> In googling UBIFS problems, I do see posts across the internet of
> UBIFS devices that will not boot after power is turned off and on. My
> experience with JFFS2 is that it has always recovered during boot with
> all the designs I have participated in over the last several years.
> Admiteddly, the act of doing something like "scandisk" on boot slows
> the boot down, but does seem to add reliability.

It has been very resilient to power failures in my experience -- the
Linux ubifs code has always managed to recover, and very quickly.

The main pitfall is that U-Boot's support for ubifs is only the
read-only subset of Linux's.  That means it can read from a consistent
ubifs partition, but not from one that needs repair (because that
requires writing).  So you can't rely on booting your Linux kernel
*from a ubifs partition*.  But if you have your kernel in a separate,
read-only uImage partition you should be fine (it's just more annoying
to update kernels).

-- 
Eric Cooper             e c c @ c m u . e d u