Exchange 2013. Are two servers really necessary?


With my past deployments of Microsoft Exchange 2010, for any site that required more than 50 users, I've ensured that we deployed 2 servers.  One for CAS & HUB, and the other for MBX role.

I am seeing that this role separation is not necessary nor recommended when deploying Exchange 2013.  

That being said, what are the considerations when determining whether I should or not?  I have a new deployment in progress.  Mailbox is about 140GB in size and we're looking at about 150 users.

Thanks in advance.

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Will SzymkowskiSenior Solution ArchitectCommented:
This question ultimately comes down to budget and availability. Meaning if your company wants to have multiple Exchange servers to ensure that your mail is highly available then implementing more than one Exchange server is required.

That being said everything comes with a cost. If your company can still function without email for a period of time if/when the Exchange server is down, then they need to make that call.

For the environment that you have mention could EASILY run on one Exchange server that has adequate resources (CPU/RAM/DISK) for 150 users with no issues at all.

So really make a business case of this and say to them, "how long could the business continue to function without email".

More servers means extra costs for OS licensing and Exchange Server Licenses for Each server you spin up. And if you are going to load balance CAS then you are recommended to use a Hardware Load Balancer. Preferably a Layer 7, but you can also get away with Layer 4 as well.

Hope this helps clear things up.

Simon Butler (Sembee)ConsultantCommented:
"With my past deployments of Microsoft Exchange 2010, for any site that required more than 50 users, I've ensured that we deployed 2 servers.  One for CAS & HUB, and the other for MBX role."

That was a total waste - I don't even consider separate servers until 500 users. At 50 I wouldn't dream of splitting the roles out. I don't even think that solution was ever recommended by Microsoft - even with Exchange 2007. It has been best practise to have all roles on all servers for a very long time.

Therefore putting high availability aside, a single server for 150 users would be fine (unless every user needs a 20gb mailbox or something outrageous).


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