* Joakim Tjernlund <joakim.tjernlund@...> [120124 02:18]:
> Ed W <lists@...> wrote on 2012/01/23 19:43:49:
[ .. ]
> > I'm doing something like this using aufs.  The performance seems "not
> > bad", but you get a couple MB or so memory hit.  (I'm using squashfs as
> > well, so unsure which causes the main memory increase).
> 
> hmm, not sure how aufs would work out. One would like to permanently delete the

aufs is A Union FileSystem.  You can have a RO "branch" (say SquashFS)
and a r/w "branch" (say JFFS2 or UBIFS.)  When you write it will write
to the r/w branch and when you read it will read from the r/w branch if
it exists, else the r/o.

So, if you want to permanently delete the old software.  Write it to the
filesystem r/w filesystem (initially or after you have the aufs mounts
mounted.)  Then you can delete from the r/w filesystem and it's gone for
good.

> old sw at some point and I don't see how, perhaps I misunderstand something?
> 
> How does aufs do w.r.t power cuts? We need a reliable FS w.r.t power cuts. In the
> past we have used JFFS2 on NOR flash and that has worked really well. Now
> we need to switch to NAND due to size requirements.

You still want to pick a r/w branch with a filesystem that handles power
cuts well.  You can continue to use JFFS2.

[..]

Todd