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I was wondering if anyone can offer some guidance on the nature of the load that is generated on a Exchange 2013 server.

The background of my question is that I'm currently considering options concerning the CPU of my servers. I have servers available to me with lower frequency but many cores, which are usually used for parallel processing workloads (Intel Xeon 1.7GHz, 20 core, 40 threads due to hyperthreading). Should I look for a more high spec CPU or will this do?

The server will host about 150 mailboxes in a corporate environment.

HopelessN00b
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bfloriang
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  • This question might be a bit too broad to fully answer. CPU frequency doesn't tell the whole story of CPU performance anymore. In looking at Exchange performance, CPU is only one area to look at but may not give you the most "bang" for the buck compared to increasing spend in other areas (memory/storage/etc). Faster is usually better, but more cores might help depending on your workload and roles on the server. 150 mailboxes doesn't tell the whole workload story either - are they heavy email users? Messages/sec? avg Message size? All will play a part. – Rex Feb 13 '15 at 21:49
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    What really matters for Exchange (and for mailservers in general) in not CPU speed, rather I/O (disk) speed. Exchange 2010+ is said to work reasonably well even on array of standard 7200 RPM disks. – shodanshok Feb 13 '15 at 22:46
  • @Rex Normally, I'd agree with you, and capacity planning or hardware spec questions are usually too broad to be answered acceptably, but I literally use more CPU on my *desktop* when I'm watching Netflix videos than our corporate Exchange server uses shuffling hundreds of thousands of emails to our ~1,000 users during business hours. So this is actually a pretty straightforward question that can be easily answered. – HopelessN00b Feb 13 '15 at 23:41

2 Answers2

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Exchange servers are generally RAM or disk-I/O bound... which should make sense, if you think about what an email server actually does - primarily, it transfers messages from one place to another, and stores them if the server is their ultimate destination. That workload isn't very computationally intensive.

The virtualized, all-roles-in-one Exchange server I administer, which serves over 1,000 users and has over 2,000 mailboxes, runs just fine on a single core from a 3.07 GHz Xeon X5675. Average CPU load during business hours is around 50% (~1.5 GHz), with occasional spikes to ~90% (~2.7Ghz) and the average CPU off-hours load is around 850 Mhz.

In line with that, minimum requirements for Exchange simply list a 64 bit compatible, non-Itanium processor. And, fortunately, modern versions of Exchange come with a pre-deployment analyzer tool you can, and should, run on your server to make sure it meets the minimum and recommended requirements, but I expect that you'd be just fine running your Exchange server on that 1.7 Ghz Xeon. In fact, I'd expect that a 20 core CPU would be heavy overkill for an Exchange server, even if it only rates at 1.7 Ghz per core.

(P.S.: Why dedicate a whole server to such a small Exchange environment? Hyper-V is free - why not virtualize it?)

HopelessN00b
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Your specifications are fine... but definitely overkill for the user/workload you're anticipating.

Please see: Exchange 2013 as VM vs Exchange Physical Server

Here's a 3-day snapshot of a very busy 200-user Exchange installation running virtualized on 4 x 2.0GHz E5-2620 CPUs and 20GB of RAM.

The workload is RAM-bound. All of the CPU cores you're planning to throw at the solution will likely be idle.

enter image description here

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ewwhite
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