Ocfs2 users - Dec 2008 - mailcluster advice?

I'm working on setting up a mail cluster (imap, pop, mx) using ocfs2.
Does anyone have any advice or experiences they'd like to share?

I've done web and video clusters before with great success, however
those were structured in a such a way that there was generally only ever
one write node active at a time and many read nodes.  Mail won't have
that feature.

It's all maildir, so there's no file locking, but one does need to be
concerned about ocfs2 lock contention.  Currently our thought is to have
one node for mx, pop, and imap each.  Ignoring pop for the moment, that
means there's potentially a source of contention on $mail_folder/new
when sendmail is pushing mail and dovecot is trying to move mail to
$mail_folder/cur.  After that imap connections should be on their own as
far as other nodes are concerned.  There may be multiple connections
from different clients to a single folder, but that's still confined to
the node serving imap, so in theory obtaining locks on the directory
should be quick.  I'm ignoring pop because the bulk of the users use
imap and those that use pop almost exclusively use pop, so the analysis
remains the same.

Thoughts?

Also, does ocfs2 support dnotify or inotify?

Thanks,
Brian

I've been wondering the same things.  Currently testing an ocfs2 filesystem
using two servers (postfix, courier imap/pop, etc) and am wondering if I'll
run into problems, especially with the simultaneous writes.  Reading the
1.4 user guide, I notice the author says the filesystem can be used for
fail-over mail facilities (but will work in read/read environments).

Currently using two Cent OS 5 servers (2.6.18-92.1.22) and:
ocfs2-tools-1.4.1-1.el5
ocfs2-2.6.18-92.1.22.el5PAE-1.4.1-1.el5
ocfs2console-1.4.1-1.el5

Searching through the archives, it appears folks are using multiple mail
servers accessing an ocfs2 backend, but with mixed results.


Brian Kroth bpkroth at gmail.com
Fri Dec 5 06:45:12 PST 2008

I'm working on setting up a mail cluster (imap, pop, mx) using ocfs2.
Does anyone have any advice or experiences they'd like to share?

I've done web and video clusters before with great success, however
those were structured in a such a way that there was generally only ever
one write node active at a time and many read nodes.  Mail won't have
that feature.

It's all maildir, so there's no file locking, but one does need to be
concerned about ocfs2 lock contention.  Currently our thought is to have
one node for mx, pop, and imap each.  Ignoring pop for the moment, that
means there's potentially a source of contention on $mail_folder/new
when sendmail is pushing mail and dovecot is trying to move mail to
$mail_folder/cur.  After that imap connections should be on their own as
far as other nodes are concerned.  There may be multiple connections
from different clients to a single folder, but that's still confined to
the node serving imap, so in theory obtaining locks on the directory
should be quick.  I'm ignoring pop because the bulk of the users use
imap and those that use pop almost exclusively use pop, so the analysis
remains the same.

Thoughts?

Also, does ocfs2 support dnotify or inotify?

Thanks,
Brian



James Moseley

jmoseley at corp.xanadoo.com wrote:
> I've been wondering the same things.  Currently testing an ocfs2
filesystem
> using two servers (postfix, courier imap/pop, etc) and am wondering if
I'll
> run into problems, especially with the simultaneous writes.  Reading the
> 1.4 user guide, I notice the author says the filesystem can be used for
> fail-over mail facilities (but will work in read/read environments).
I mentioned failover as most mailservers are not cluster-enabled.
But I will be happy to be corrected.