Am 31.10.2011 10:43, schrieb Arlin:

Hi Robert,

Thanks for the reply. We are upgrading Dovecot to v2.0.15 and other component's to the latest version. In that case, can we use san for storage or are you recommending that drbd with ocfs2 is the best way to attain the horizontal scalability for the mail storage?

Hi Arlin, there is no best way, you should choose whatever fits best to your needs an haves so it depends on many stuff ( i.e at last finance, network, manpower, knowledge) etc

So all i can say iam just using a loadbalanced cluster setup with drbd ocfs2 maildir dovecot postfix mysql clamav spamassassin on ubuntu lucid lts with 3000 Mailboxes without any big Problems yet but i can imagine that a professional SAN might be better in performance but there is a lot other other questions left , i.e maildir must not be the best solution for mailbox format etc

cluster setups with lots of mailboxes are complex in many ways, if you planning a real big mailservice you should ask more here on this list for existing other setups and choose i.e Timo and/or others for professional and paid advice and work

Thanks, Arlin

-----Original Message----- From: dovecot-bounces@dovecot.org [mailto:dovecot-bounces@dovecot.org] On Behalf Of Robert Schetterer Sent: 31 October 2011 14:26 To: dovecot@dovecot.org Subject: Re: [Dovecot] How can we horizontally scale Dovecot across multiple servers?

Am 31.10.2011 09:47, schrieb Arlin:

...

Could anyone please respond to this query. Thank you!

you may use loadbalancers i.e (keepalived etc) and/or

http://wiki2.dovecot.org/FeatLoginProxy http://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy

look the list for cluster setups etc

reading your former post you want to use many outdated prog versions dont do that a san for storage might be a good choice some of the list use drbd with ocfs2 and other cluster filesystems

...

From: Arlin [mailto:arlin@mvs.us] Sent: 28 October 2011 17:06 To: 'dovecot@dovecot.org' Subject: How can we horizontally scale Dovecot across multiple servers?

Hi,

How can we horizontally scale Dovecot across multiple servers? Do we require to install independent instances of Dovecot on each server?

We are planning to use a NAS/SAN device using ZFS or EFS for email

storage.

...

Each logical unit will be of 10TB and similarly as the no: of user increases we are planning to add multiple 10TB units.

In this case how we can manage the email storage on multiple volumes from Dovecot.

The configuration of our existing system is:-

Dovecot 1.0.15 / Maildirs

Postfix 2.5.5

Debian 5.0.9 (Lenny)

MySQL 5.0.15

Please advise.

Thanks in advance.

Creative Regards,

Arlin

-- Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria

-- Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria

Am 31.10.2011 12:28, schrieb Felipe Scarel:

Quick question about the usage of DRBD: I'm thinking of a setup on my organization here (15k+ users, 4TB of email data), but I'm holding back on the clusterization due to the high volume of data.

Using DRBD would implicate mirroring those 4TB of data across all cluster nodes? If yes, I might go with a SAN-based solution, though I haven't studied much about that setup yet (the other sysadm administrates the VMs and SAN, gotta ask him a few questions).

i wouldnt do that with drbd as such big setup , there should be enough money using better choices

On Mon, Oct 31, 2011 at 08:00, Robert Schetterer mailto:robert@schetterer.org> wrote:

Am 31.10.2011 10:43, schrieb Arlin:
> Hi Robert,
>
> Thanks for the reply. We are upgrading Dovecot to v2.0.15 and other
> component's to the latest version. In that case, can we use san
for storage
> or are you recommending that drbd with ocfs2 is the best way to
attain the
> horizontal scalability for the mail storage?

Hi Arlin, there is no best way, you should choose
whatever fits best to your needs an haves
so it depends on many stuff ( i.e at last finance, network, manpower,
knowledge) etc

So all i can say iam just using a loadbalanced cluster setup with drbd
ocfs2 maildir dovecot postfix mysql clamav spamassassin on ubuntu lucid
lts with 3000 Mailboxes without any big Problems yet
but i can imagine that a professional SAN might be better in performance
but there is a lot other other questions left , i.e maildir must not be
the best solution for mailbox format etc

cluster setups with lots of mailboxes are complex
in many ways, if you planning a real big mailservice
you should ask more here on this list for existing other setups and
choose i.e
Timo and/or others for professional and paid advice and work


>
> Thanks,
> Arlin
>
> -----Original Message-----
> From: dovecot-bounces@dovecot.org
<mailto:dovecot-bounces@dovecot.org>
[mailto:dovecot-bounces@dovecot.org
<mailto:dovecot-bounces@dovecot.org>] On
> Behalf Of Robert Schetterer
> Sent: 31 October 2011 14:26
> To: dovecot@dovecot.org <mailto:dovecot@dovecot.org>
> Subject: Re: [Dovecot] How can we horizontally scale Dovecot
across multiple
> servers?
>
> Am 31.10.2011 09:47, schrieb Arlin:
>> Could anyone please respond to this query. Thank you!
>
> you may use loadbalancers i.e (keepalived etc) and/or
>
> http://wiki2.dovecot.org/FeatLoginProxy
> http://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy
>
> look the list for cluster setups etc
>
> reading your former post
> you want to use many outdated prog versions dont do that a san for
storage
> might be a good choice some of the list use drbd with ocfs2 and other
> cluster filesystems
>
>>
>>
>>
>> From: Arlin [mailto:arlin@mvs.us <mailto:arlin@mvs.us>]
>> Sent: 28 October 2011 17:06
>> To: 'dovecot@dovecot.org <mailto:dovecot@dovecot.org>'
>> Subject: How can we horizontally scale Dovecot across multiple
servers?
>>
>>
>>
>> Hi,
>>
>>
>>
>> How can we horizontally scale Dovecot across multiple servers? Do we
>> require to install independent instances of Dovecot on each server?
>>
>>
>>
>> We are planning to use a NAS/SAN device using ZFS or EFS for email
> storage.
>> Each logical unit will be of 10TB and similarly as the no: of user
>> increases we are planning to add multiple 10TB units.
>>
>> In this case how we can manage the email storage on multiple volumes
>> from Dovecot.
>>
>>
>>
>> The configuration of our existing system is:-
>>
>>
>>
>> Dovecot 1.0.15 / Maildirs
>>
>> Postfix 2.5.5
>>
>> Debian 5.0.9 (Lenny)
>>
>> MySQL 5.0.15
>>
>>
>>
>> Please advise.
>>
>>
>>
>> Thanks in advance.
>>
>>
>>
>> Creative Regards,
>>
>> Arlin
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
> --
> Best Regards
>
> MfG Robert Schetterer
>
> Germany/Munich/Bavaria
>


--
Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria

-- Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria

On 31/10/2011 11:28, Felipe Scarel wrote:

Quick question about the usage of DRBD: I'm thinking of a setup on my organization here (15k+ users, 4TB of email data), but I'm holding back on the clusterization due to the high volume of data.

Using DRBD would implicate mirroring those 4TB of data across all cluster nodes? If yes, I might go with a SAN-based solution, though I haven't

I don't the technique with DRBD is something like having pairs of machines, each of which is a backup for the other. There were some old notes on the Dovecot website about such a setup?

Roughly I seem to recall that each pair of machines ran two virtual machines, each of which ran active on one of the nodes each, but could migrate to the other if needed. Add a bunch of such paired nodes to get to the performance you require and put a dovecot proxy instance in front of the whole lot

In contrast the SAN solution uses a clustered filesystem (opinion varies on which performs best) and then in theory every machine has access to every mailbox. In practice access to the SAN is relatively slow compared with local storage, so the technique seems to be to store indexes on the local machine and then using the front end proxy to be somewhat "sticky" in returning users to the same backend node so that the indexes can be re-used and not rebuilt

The DRBD solution offers local disk access speed to the node and would on the surface give far faster performance (if disk were the limiting issue). However, it's likely to be more complex to maintain and manage and without buying licences you get only failover between pairs of machines. The SAN solution in theory looks like perfect scale up, big backend and just add more backend IMAP nodes as you need them, and all the clever stuff moves to the frontend load balancer to be "sticky" and obviously that's your main maintenance problem.

However, based on evidence from users of big systems, IO is likely to be your main bottleneck and so just theoretically, the SAN will only scale as far as it doesn't run out of IOs... Using local disk for indexes would tend to reduce the amount of IOs needed (from the SAN) very dramatically, but you still have some limit out there and it's a question of whether you will reach it? DRBD has theoretical infinite scale out because each time you add another pair you get more IO as well as more CPU

I don't have the fortune to have anything like the volume of users you have so I have no opinion to offer... However, I think the above accurately summarises your options. Others might help clarify the likely bounds on performance of each solution and maintenance headaches (eg some have had problems with maildir mounted on OCFS/GFS2 and fixed that by moving to dbox, etc)

Please report on your results! Good luck

Ed W