[Imap-uw] imap without nfs
richard at ics.mq.edu.au
Mon Feb 18 04:54:27 PST 2008
For many years we have been running a uw-imap service for our
department servicing a few hundred users reasonably successfully.
The system has evolved though various incarnations as we improve
things, however it still employs nfs. Clearly, the advice of
this list is 'When building your mail infrastructure DONT use NFS!'
so I'm looking for recommendations on how to keep nfs out of the
Our current setup is box dedicated to imap/pop with a local /var/mail
containing all users' inboxes. Inbound mail is dropped in /var/mail
by a local sendmail. No NFS so far ...
Users access their mail via imap (as they should) or pop (if they must)
through a variety of clients (eg Pine, Thunderbird, Outlook, Webmail
etc etc etc). No NFS here either ...
Our outbound mail (ie users smtp server), spam/av scanning, listserving
and our mail gateway service are all handled by other separate boxen.
This keeps things nicely decoupled and all is well. Still no NFS ...
Our users' home directories live on another box which contain the
.forward, .procmail etc, files plus users' personal imap store (ie ~/mail).
Clearly these files need to be visable to the mailserver which is
where the bad evil nfs bit comes in.
There seems to be a couple of strategies we could employ to remove
this final dependancy on nfs - but none of the below seem ideal.
1. Make the home directory server and the imap server one and
the same box. Obviously we'd like to keep services as separate
as possible for all the obvious reasons - so this option is
not overly attractive
2. Turn the imap service into a black box. This would involve
provisioning each user with a separate home directory locally
on the imap server for their personal imap store and the various
.dot files sendmail would like to see, plus anything procmail
might like to see. Then we'd then have to come up with a way
for users to manage their .dot files inside the black box which
is getting complicated and not very transparent for users.
3. Locally mount a personal imap store filesystem on our imap server
and provision each user with a directory within this store. Then
replace each user's ~/mail directory with a symlink to the appropriate
directory on the local store. This way all users home directories
can remain nfs mounted (and procmail etc will be happy) and the
imap daemons only ever interact with local files. We have used this
arrangement in the past quite successfully to address performance
problems relating to users with large personal imap stores but it
is somewhat inelegant.
If people have a better approach we'd be very interested to hear - or maybe
someone can tell us that our current use of nfs is not that tragic since
all our imap daemon run on the same box hence no distributed locking issues.
Thanks in advance.
Computing Technical Services - ICS, Macquarie Uni - Syd, Aust
Email: richard at ics.mq.edu.au, Ph: +61 2 98509587, Fax: +61 2 98509551
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