Keep Exchange Server functions separate or together?

Greetings all and a good new year to everyone.

I am setting up a test environment for implementing Exchange 2010 under VMware 5 environment.  Among others sources I have downloaded is an article from VMware covering Best Practices for Exchange 2010 on VMWare:

FYI this is an excellent article for anyone looking for reference materials on this implementation.

My question is whether industry practice leans towards setting up the Hub Transport, Mailbox and CAS servers as separate VM's, or if it is recommended to combine 2 or more functions in a single VM.  My client base is in the SMB market, so the number of users for a given client would range from min. 5 to up to 75 users.  I will be migrating all existing Exchange 2003 + Windows 2003 environments to 2010 and VMware in the next few months.  I don't anticipate budget issues in acquiring the necessary (Dell) hardware for any given implementation.

As this is purely a recommendation question, I am setting the points at 150.

Thanks in advance

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Will SzymkowskiSenior Solution ArchitectCommented:
Really there is no "best practice" for this situation. Back before Exchange 2013 came out it was always apparent to have mailbox servers on their own and have CAS/HUB on the same server.

With the release of Exchange 2013 they have recommeded to leave the roles all on the same sever due to the new arcitecture with Exchange 2013.

Both ways will work but if you split the roles you will have to pay for additonal licensing for your servers. If you keep the roles on the same server you will save on the cost for that.

However you will not be able to use WNLB and DAG on the same server if you install all of the roles on a single server. Most organizations use a Vitrual Load balancer or a physical load balancer to take care of this. WNLB is not supported in a production environment.

I personally like to split the roles apart in earlier version of Exchange (prior to Exchange 2013) which i beleive it is easier to troubleshoot is any issues arise.

That being said both ways will work but you have a limitation if you are going to use DAG and WNLB on the same server you cannot if roles are all on a single server.


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Speaking strictly from an exchange, it's very common to have multiple roles on a single server.  The following blog entry does a pretty good job of covering this:

Depending on the size of your organization, it may still be viable to combine the roles down.  If you were to split each role off onto a different VM "just because you can", you will have the operating system overhead on each VM, meaning more power on your VM Host server is being wasted for overhead (though VM technology is improving rapidly).
While this is a very technical article (TechNet), it covers the points of Exchange 2010 Virtualization (some of which Spec mentioned) and is also worth a read if you haven't seen it.

I also just saw that you have a very small user base.  If it were me, I would still pursue multi role servers.
Simon Butler (Sembee)ConsultantCommented:
The best practise now is to no longer separate the roles. I haven't separated them for well over three years. This is even on very large deployments.
All roles on all servers.

The only reason that people still separate out the roles is to use Windows Network Load balancing. However WNLB is very poor and not recommended by the Exchange product team. Much better if you need to use multiple servers to save the money from additional Exchange licences and deploy a hardware (or virtual hardware based) load balancer.

At less than 500 users I wouldn't even consider splitting the roles out, there is no benefit.

jkirmanPrincipalAuthor Commented:
Thanks to all for your responses.  I've raised the overall point total to 500 and split it across the 4 responses.  You've collectively indicated that splitting out roles ends up with increased overhead, licensing etc.  and that WNLB should not be used.  The links offered look quite helpful.  Thanks to Spec01 for mentioning that all roles on 1 server will prohibit use of DAG.  Will continue research and testing but appreciate all responses.  Wishing a good Monday to all,

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