[Dovecot] Design details of high performance dovecot cluster

[Robert Schetterer]

Am 06.12.2013 13:06, schrieb JEHERUL:
> Hi Robert,
> 
> Thanks for your quick reply. I have already read the document you have
> mentioned  but I am unable to come to any decision.
> 
> At present we have ext4 file system in our storage. So it is not
> possible to use NFS at our present situation. I think we should migrate
> to GFS2 or glusterfs. But lots of people in mailing list raising
> question about the performance issues of NFS. I am really confused about
> it.
> 
> Can you share some design document for load balancing or clustering ...
> 
> Regards
> 
> Jeherul

Hi Jeherul,


this is a importend sentence

http://wiki2.dovecot.org/Director

...
As long as user has simultaneous connections, the user is always
redirected to the same server
...


but however before doing else you should find the bottleneck
with your san ext4 and/or your dove install !!!!


i dont recommand gfs2 or glusterfs ( for reporting problems, which may
recently get fixed ),

i am running ocfs2 on drbd master/master for 5000 mailboxes a 0.5 GB
maildir store behind keepalived loadbalancers

like

http://major.io/2011/02/13/dual-primary-drbd-with-ocfs2/


but these days i might would switch to sdbox format and doing different
things

there are people have up and running nfs setups fine, too

also i tested ceph storage

http://sys4.de/en/blog/2013/06/06/postfix-dovecot-ceph-cluster-storage/

i am sorry there is no general advice for this case , it depends on your
needs , haves , budget ,knowledge

But youre right, io performance on storage is a important point ever, so
whatever you do ,you always hat to deal with it

look into list archive about existing "cluster" solutions

if you need more advice from the list you have to post more detailed
bug description, config, logs

> 
> 
> On Fri, Dec 6, 2013 at 4:42 PM, Robert Schetterer <rs at sys4.de
> <mailto:rs at sys4.de>> wrote:
> 
>     Am 06.12.2013 11:28, schrieb JEHERUL:
>     > Dear All,
>     >
>     > Currently we are running a mail system for 10000 users each 2GB
>     mailbox. At
>     > present we have 5 mail servers where users mailboxes are
>     distributed almost
>     > uniformly.
> 
>     looks enough
> 
>     We have a HP SAN Storage (HP EVA 6400) where mailboxes are
>     > stored. We partition the storage into five vg and each is mounted
>     on the 5
>     > servers. We are using postfix and dovecot.
>     >
>     > The system was running fine but currently we  notices high IO load
>     due to
>     > IMAP connection. So we are planning to build a dovecot cluster.
> 
>     ident the io problem on the storage, give more info about  mailbox
>     format etc
> 
>     perhaps read
> 
>     http://wiki2.dovecot.org/MailLocation/SharedDisk
>     http://wiki2.dovecot.org/NFS
> 
> 
>     >
>     > Please suggest some design for the dovecot cluster keeping in mind
>     to our
>     > scenario. (If needed we can buy additional hardware like load
>     balancer).
> 
>     you should use loadbalancer, you dont have to buy it , something like
>     keepalived etc is enough, however you should use
> 
>     http://wiki2.dovecot.org/Director with more servers
> 
>     for an idea with loadbalancers look at
> 
>     http://sys4.de/de/blog/2013/06/10/loadbalancing-mit-keepalived-postfix-dovecot/
> 
>     ( sorry german only )
> 
>     >
>     > With Thanks and Regards
>     >
> 
>     at last
>     you have to give more info like dovecot version , config
>     logfiles , general setup
> 
> 
> 
> 
>     Best Regards
>     MfG Robert Schetterer
> 
>     --
>     [*] sys4 AG
> 
>     http://sys4.de, +49 (89) 30 90 46 64
>     Franziskanerstraße 15, 81669 München
> 
>     Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263
>     Vorstand: Patrick Ben Koetter, Axel von der Ohe, Marc Schiffbauer
>     Aufsichtsratsvorsitzender: Florian Kirstein
> 
> 
> 
> 
> -- 
> Jeherul Islam
> Scientific Officer
> Computer Centre
> Indian Institute of Technology Guwahati
> Guwahati-39
> India
> Office No :+91-361-258-3353
> 



Best Regards
MfG Robert Schetterer

-- 
[*] sys4 AG

http://sys4.de, +49 (89) 30 90 46 64
Franziskanerstraße 15, 81669 München

Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263
Vorstand: Patrick Ben Koetter, Axel von der Ohe, Marc Schiffbauer
Aufsichtsratsvorsitzender: Florian Kirstein