Messages in this thread | | | From | Al Boldi <> | Subject | Re: [RFC] VFS: FS CoW using redirection | Date | Sun, 9 Jul 2006 15:50:36 +0300 |
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Eric Van Hensbergen wrote: > On 7/8/06, Al Boldi <a1426z@gawab.com> 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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