[Ocfs2-users] Shared Writeable MMAP

[Joel Becker]

On Wed, Jun 12, 2013 at 02:27:05PM +0200, Robert Schetterer wrote:
> Hi @ll i have a question about feature
> Shared Writeable MMAP and its relation to concurent file use.
> 
> Background, over years i am hosting dovecot imap servers behind
> loadbalancers on a drbd master/master setup shared formated storage
> ocfs2 1.4.3 maildir without problems.
> 
> the dovecot wiki says
> 
> http://wiki2.dovecot.org/Director
> 
> Director can be used by Dovecot's IMAP/POP3/LMTP proxy to keep a
> temporary user -> mail server mapping. As long as user has simultaneous
> connections, the user is always redirected to the same server. Each
> proxy server is running its own director process, and the directors are
> communicating the state to each others. Directors are mainly useful for
> setups where all of the mail storage is seen by all servers, such as
> with NFS or a cluster filesystem
> 
> so the director service is most installed on the loadbalancers mainly
> with nfs storage, proved to be a "must have"
> 
> after online investigation and long lasting reality tests , i guess "or
> a cluster filesystem " isnt true for ocfs2, cause on drbd it works fine
> with concurent files use ( i.e mailbox format maildir ) by feature
> Shared Writeable MMAP.
> 
> Can sombody confirm this, or teach in easy words how it works ( or not )
> and why ?

	I'm not sure what you are asking.  I *think* you are saying,
"ocfs2 is not a sufficient cluster filesystem for Dovecot, because it
does not have shared writeable mmap(2)."  If that's what you are saying,
then you are incorrect.  Shared writeable mmap(2) is a very standard
feature of ocfs2; we can't be POSIX without it.
	I also don't understand how you are configured.  Because it
sounds like you are using ocfs2+drbd successfully, which conflicts with
your statement that ocfs2 is not a sufficient cluster filesystem.

Joel

> 
> 
> Best Regards
> MfG Robert Schetterer
> 
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