[Dovecot] nfs director

[Noel Butler]

On Sat, 2010-08-28 at 09:18 +0200, Cor Bosman wrote:

> Noel, I think you just dont quite understand the problem the director is
> solving. 
> 
> The issue is that NFS is not lock-safe over multiple servers. We have 35
> imap servers accessing a central NFS cluster. (we have over a million
> mailboxes) We offer IMAP to end user clients, and through webmail. This means
> that users are more and more likely to have multiple mail clients open.
> 


we have a some total of 2 imap servers, only used for webmail, so it is
not a problem for us, at all, period.
director will not solve those inbound mail server issues, the REAL issue
at hand here being discussed, and anyone not knowing this should not be
partaking in this thread.


> This is not farfetched. This is normal behavior when you start offering
> IMAP access. 
> 


imap access is not common in this country, it is in fact extremely rare,
common only for webmail servers.


> All these 3 sessions want to update the index files. (im current not including


not an issue as I previously stated (twice I believe) as we do not
permit multi session logins


> dovecot LDA, which also wants to update the index files). Because of issues

funny how postfix doesnt have this issue, qmail doesnt have this issue
nor does exim (never ran sendmail in this config only a crazy person
would use mbox over NFS)



> Now there is a workaround. NFS locking can be made to work better if all
> processes trying to access the NFS indexes are on the same machine. So


there certainly is a workaround, its called, in our case, use postfix's
deliver, which under my instruction has already happened on half the
servers since it is clear this issue will not ever be solved in dovecot.


> 
> What the dovecot director is doing is ensuring that sessions from the same
> user all get directed to the same imap server, so NFS locking works safely.
> 


yes, this has been mentioned some 40 times already, you know, i do
actually know this, however that will NOT solve the problem as outlined
earlier, the director by Timos admission will NOT load balance users in
its current state, nor will it load balance inbound connections.


> I wish my foundry could do this, so I wouldnt need the director, but alas,
> it cant. If you operate a situation like im describing above, you WILL need
> the director, or accept that your users may run into problems reading their
> mail. 
> 


well they aint needed it since 2003, nothings died, broken, crashed,
caused hurricanes, droughts, whatever, so, cant see why all of a sudden
they will now.