Re: [9fans] QTCTL?

["Francisco J Ballesteros" <nemo@lsub.org>]

It´s not "synthetic vs stored on disk".
It´s "behaves like a file vs does not".

For example, some files in omero may be large (images)
and it´s nice to cache them. But some files do not behave as files
(you open OTRUNC, rewrite, and might read something else from it later)

In the octopus we mount devices, yet we want to cache most
of their structure/data.

For a local area network, it´s ok to say "do not cache at all".
But IMHO, for a wide area network, or slow adsl lines, it´s not so ok.

Regarding coherency, you always have races, you have to reach
the server anyway and that takes time. But in many cases this is not
a problem. When it is, I agree that you have to use something else or
put something else within the file server involved.



On 10/31/07, Russ Cox <rsc@swtch.com> wrote:
> Plan 9's default is not to cache,
> making a "don't cache this" bit
> unnecessary.  If the user explicitly
> requests caching (by using cfs, say),
> then he's responsible for making sure
> it is appropriate.
>
> If I tell the computer to cache /net,
> that's not the computer's problem,
> any more than if I bind /proc /net.
>
> Since there's no coherence protocol
> anyway, caching can't be done automatically.
> It might give the right answer most of
> the time, but it will screw up corner cases
> and make the system more fragile.
>
> This whole synthetic vs not mentality
> is Unix brain-damange.  On Plan 9 there
> is no distinction.  Everything is synthetic
> (or everything is not, depending on your
> point of view).
>
> Russ
>