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From: Aaron Wolfe on 12 Feb 2010 17:17
On Fri, Feb 12, 2010 at 4:50 PM, Jonathan Tripathy <jonnyt(a)abpni.co.uk> wrote:
> Hi Everyone,
>
> Thanks for all the comments.
>
> The reason why I said 256MB RAM, is because that is currently what my VM
> has...
>
> If I were to take out a dedicated server with:
>
> 2.8 Dual Core
> 2GB RAM
>
> how much would that handle?
>
> My customer is a business, with 600 staff, however I think they just use a
> single broadband connection so that will be the limiting factor, as this
> dedicated server has a 100Mbps link to the net..
>
> Please let me know what you think
>

If you want to give your client good advice, you will have to measure
their mail flow in a meaningful way.
How many messages per second, minute, hour, day do you need to handle?
How many concurrent SMTP sessions? Do they even care if a message
takes 100ms vs 100 seconds to traverse this system?

> Thanks
>
> Jonny
>
> On 12/02/2010 19:24, Victor Duchovni wrote:
>
> On Fri, Feb 12, 2010 at 05:14:30PM -0000, Jonathan Tripathy wrote:
>
>
>
> My current server has 256MB RAM (It's a VM on slicehost). How many users do
> you think that will handle?
>
>
> Is more RAM substantially more expensive? 256 MB is rather meek these days.
> With physical servers, one typically gets 16GB or more of RAM these days.
> Even a 6-Watt Atom-CPU FitPC box comes with 1GB of RAM! Your machine is
> way off the mainstream memory curve... For Postfix alone you're fine, but
> for running an IMAP server with users, you are likely too cramped, ask
> on the Dovecot list, not here. Postfix is not very memory intensive.
>
>

From: Victor Duchovni on 12 Feb 2010 17:41
On Fri, Feb 12, 2010 at 05:17:26PM -0500, Aaron Wolfe wrote:

> If you want to give your client good advice, you will have to measure
> their mail flow in a meaningful way.
> How many messages per second, minute, hour, day do you need to handle?
> How many concurrent SMTP sessions? Do they even care if a message
> takes 100ms vs 100 seconds to traverse this system?

No, this is largely irrelevant. What matters is the IMAP performance
they expect, that IMAP servers are reasonably CPU and memory intensive.

--
Viktor.

P.S. Morgan Stanley is looking for a New York City based, Senior Unix
system/email administrator to architect and sustain our perimeter email
environment. If you are interested, please drop me a note.

From: Stan Hoeppner on 12 Feb 2010 18:01
Jonathan Tripathy put forth on 2/12/2010 3:50 PM:

> 2.8 Dual Core
> 2GB RAM

What about disk? Disk is typically the key subsystem for mail performance.
Fast CPUs don't do much for mail without a fast disk subsystem. At minimum get
hardware mirroring for two disks (RAID 1) and best to make them 10K or 15K rpm
models. 7.2K rpm disks might not cut it for 600 users unless you go hardware
RAID 10 with 4 disks.

> how much would that handle?

With the right disk subsystem, those specs above with Postfix + Dovecot IMAP +
antispam stuff + etc should be plenty.

> My customer is a business, with 600 staff, however I think they just use
> a single broadband connection so that will be the limiting factor, as
> this dedicated server has a 100Mbps link to the net..

What is the up/down link speed of the broadband connection? If's it's something
like the low ball minimum 1.5M/512K the speed of the server won't mean much,
just as you surmise. And if that is the case, this smtp/imap server should be
placed on site at the business location, not in a colo.

Where is their current mail server located? Also, you need to get some usage
data from their current server to find out exactly what their flow volume is.

--
Stan

From: Aaron Wolfe on 12 Feb 2010 18:24
On Fri, Feb 12, 2010 at 5:41 PM, Victor Duchovni
<Victor.Duchovni(a)morganstanley.com> wrote:
> On Fri, Feb 12, 2010 at 05:17:26PM -0500, Aaron Wolfe wrote:
>
>> If you want to give your client good advice, you will have to measure
>> their mail flow in a meaningful way.
>> How many messages per second, minute, hour, day do you need to handle?
>>  How many concurrent SMTP sessions?  Do they even care if a message
>> takes 100ms vs 100 seconds to traverse this system?
>
> No, this is largely irrelevant. What matters is the IMAP performance
> they expect, that IMAP servers are reasonably CPU and memory intensive.
>

I was speaking about Postfix. Of course other software will have its
own requirements.
If spam filtering is going to be used, it would be wise to consider
those requirements as well.
On my largest server we do not use any IMAP software, but we do use
spamassassin. SA uses considerably more resources than Postfix per
SMTP process.

> --
>        Viktor.
>
> P.S. Morgan Stanley is looking for a New York City based, Senior Unix
> system/email administrator to architect and sustain our perimeter email
> environment.  If you are interested, please drop me a note.
>

From: Victor Duchovni on 12 Feb 2010 21:34
On Fri, Feb 12, 2010 at 06:24:59PM -0500, Aaron Wolfe wrote:

> If spam filtering is going to be used, it would be wise to consider
> those requirements as well.

A host with 256MB of RAM is not going to be doing much heavy lifting
with content inspection.

--
Viktor.

P.S. Morgan Stanley is looking for a New York City based, Senior Unix
system/email administrator to architect and sustain our perimeter email
environment. If you are interested, please drop me a note.

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