[Dovecot] dovecot 2.1.5 performance

Joseba Torre joseba.torre at ehu.es
Wed Jun 20 12:58:05 EEST 2012

El 20/06/12 11:46, Angel L. Mateo escribió:
> On 20/06/12 11:40, Angel L. Mateo wrote:
>> Hello,
>> I'm migrating from 1.1.16 running in 4 debian lenny servers
>> virtualized with xenserver and 1 core and 5GB of RAM to 2.1.5 running in
>> 4 ubuntu 12.04 servers with 6 cpu cores and 16GB of RAM virtualized with
>> VMWare, but I'm having lots a performance problems. I don't think that
>> virtualization platform could be the problem, because the new servers
>> running in xenserver has the same problems than running in vmware.
>> I have about 70000 user accounts, most of them without real
>> activity (they are students who doesn't read his email or have its
>> account redirected to other provider). I have about 700-1000 concurrent
>> imap connections.
>> I have storage in nfs (nfsv3, the nfs server is a celerra), but
>> indexes are in local filesystems (each server has its own index fs).
>> Mailboxes are in maildir format.
>> Old servers and actual director servers are load balanced with an
>> radware appdirector load balancer (the new backend servers don't need to
>> be balanced because I'm using a director farm)
>> In the old platform I have scenario number 2 described at
>> http://wiki2.dovecot.org/NFS, but in the new ones I have a director
>> proxy directing all connections from each user to the same server (I
>> don't specify any server for the user, director selects it according to
>> the hash algorithm it has).
>> Some doubts I have for the recommended in that url:
>> * mmap_disable: both single and multi server configurations have
>> mmap_disable=yes but in index file section says that you need it if you
>> have your index files stored in nfs. I have it stored locally. Do I need
>> mmap_disable=yes? What it's the best?
>> * dotlock_use_excl: it is set to no in both configurations, but the
>> comment says that it is needed only in nfsv2. Since I have nfs3, I have
>> it set it to yes.
>> * mail_nfs_storage: In single server is set to no, but in multi server
>> it set to yes. Since I have a director in front of my backend server,
>> what is the recommended?

As I see it, director ensures that only 1 server is accesing any given 
file, so you don't need any special conf (so mmap_disable=no & 

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