Eric Van Hensbergen wrote:
> On 7/8/06, Al Boldi <a1426z@xxxxxxxxx> wrote:
> > Copy on Write is a neat way to quickly achieve a semi-clustered system,
> > by mounting any shared FS read-only and redirecting writes to some
> > perClient FS.
> >
> > Would this redirection be easy to implement into the VFS?
>
> There are a variety of solutions that have been proposed or are
> available to do this sort of thing. You may want to start by looking
> at unionfs and mapfs. There are also folks looking at doing this from
> the block layer (look at the dm-userspace + cowd as well as evms and
> lvm snapshots).
The idea here, is to do things completely transparent while being as
unintrusive as possible, by relying on the current FS infrastructure, w/o
introducing another VFS.
Consider something simple like this:
VFS - anyFS1 (r/w) used normally, unless ENotFound, then redirect read to
\ anyFS2, or CoW from anyFS2 to anyFS1.
anyFS2 (r/o) used normally.
i.e: Does the VFS provide hooks for perMount Handlers?
Thanks!
--
Al
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