Excerpts from transarc.external.openafs: 17-Dec-02 Re: [OpenAFS] Cache Consist.. Paul
[EMAIL PROTECTED] (5759*)
Ka�an Co�kun wrote:
> Hi All,
>
> We are having some cache consistency problems. Sometimes the afs
> client on our web server does not represent the actual files on the
> some volumes. That is when someone uploads a new file to his directory
> the file is not noticed on the client side. The volume is a read/write
> volume. And the problem can be overcomed by creating a file on the
> volume using the client and also flush commands work too.
AFS (and OpenAFS) provides open/close consistency, not read/write consistency. After
a file is written and closed, a new open() on any client will see the fresh data. The
mechanism in use here is the callback that Paul Blackburn mentioned. The problem is
likely that the web server is caching the opens on the files that it is serving, so it
is not seeing (serving) the fresh data. If the web server shares a client cache with
the updater, they both will see the same data, as you noticed. So basically the web
server is keeping a cache of open files that is overriding the usual AFS mechanism for
automatically noticing the fresh data. By contrast, DCE/DFS provides read/write
consistency, so after a write() completes, a read() on any client retrieves fresh data.
Craig
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