UBIFS question

[Martin Townsend]

Hi,

I have an board with a 512MB Raw NAND flash memory device and 4GB
Managed eMMC flash memory device.  I would like to take advantage of
this and maintain a root filesystem on each and keep them in sync so
upgrades will upgrade each filesystem.  I can then use one of them as
a redundant image that can be used to correct the primary one or fail
over on device failure.  I have UBIFS on the raw NAND flash and ext3
on the eMMC flash.  My first thought was can I create a mirror using
raid but after researching it looks like the linux SW raid, although
very flexible, only supports block devices which rules out UBIFS.  I
could see some mails about a block device layer for UBI but I seem to
remember that this was read only or had certain restrictions.

Next I thought about maybe using Docker so I could switch between the
2 filesystems but saw a mail that UBIFS doesn't support WHITEOUT
feature that docker would require from the underlying filesystem as it
uses union/overlay filesystems.

Just wanted to check that these assumptions are correct and I haven't
missed something and also if anyone knows of another method I would be
very interested in hearing it.

Thanks in Advance,
Martin.