[Unionfs] Re: unionfs, cow, and whiteout

[pascal at pabr.org]

Paul Albrecht wrote:
> I think the 2-branch configuration where one branch is ro and the other
> is rw is the normative case and the other scenarios are more
> hypothetical than real world.

I am trying to use unionfs for hierarchical storage management:
Multiple rw branches, each with distinct storage type and
backup policies.  I want to explicitly assign files and
directories to specific branches.  For example:

myproject/src/        on a RAID1 array with weekly snapshots.
myproject/downloads/  on a regular disk with monthly backups.
myproject/build/      on a fast disk without backups.

This is actually much simpler than a liveCD - whiteouts and CoW
are not even needed.  But unfortunaly some recent simplifications
have made it harder to use unionfs with multiple rw branches for
this kind of application.

So please do not focus too much on the liveCD scenario !

Regards,
Pascal