[dovecot] Re: Architectural questions

[Thomas Wouters]

On Sat, Oct 19, 2002 at 05:01:55PM +0300, Timo Sirainen wrote:

> If your clusters access the files through NFS, there should be no
> problem. Except I've never tried Dovecot through NFS, and I'm not sure
> how well mmap()ing works through NFS. I know there's been problems
> before but hopefully they've been fixed already.

Hmm. I'm not sure what kind of behaviour you're looking for, but here's what
I see, using a little Python script on our FreeBSD servers with a
netapp-mounted filesystem. Mapping MAP_SHARED and PROT_READ|PROT_WRITE, two
different machines mounting the same directory, two processes on each
machine mmap()ing the same file.

When one process alters the data, the other process on the same machine sees
it instantly. The processes on the other machine do not see it at all, not
even when re-opening the mmap or being restarted. After doing an msync() in
the process that altered the data, the processes on the other machine still
don't see the change; they have to re-open the mmap or be restarted before
they see the change -- but when one of the processes re-opens or restarts,
the other does see the change without doing anything.

-- 
Thomas Wouters <thomas at xs4all.net>

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