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 mailto:rs@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

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-- 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