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SubjectRe: [RFC 12/26] ext2 white-out support
On Wed, Aug 01, Erez Zadok wrote:

> There are three other reasons why Unionfs and our users like to have
> multiple writable branches:
>

...

> And yes, it does make our implementation more complex.

And error-prone and unflexible wrt to changes. When XIP was introduced,
unionfs crashed all over this changes. I don't know if this has changed
yet. Not speaking of other issues like calling back into VFS (stack usage),
locking problems and so on.

> 3. Some people use Unionfs in the scenario described in point #2 above, as a
> poor man's space- and load- distribution system. Some of our users like
> the idea of controlling how much storage space they give each branch, and
> how much it might grow, and even how much CPU or I/O load might be placed
> on each of the lower filesystems which serve a given branch. That way
> they worry less about the top-layer's space filling up more quickly than
> expected. Now Unionfs was never designed to be a load-balancing f/s (we
> have RAIF for that, see <http://www.filesystems.org/project-raif.html>),
> but users seems to always find creative ways to [ab]use one's software in
> ways one never thought of. :-)

And this has nothing to do with unioning ...

> BTW, does Union Mounts copyup on meta-data changes (e.g., chmod, chgrp,
> etc.)?

No. But it was proposed during on of the last postings.
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