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Memory and CPU requirements for Exch 2010 DAG

I just wanted to put this out there and see what kind of setup I would need, approx., for memory and CPU..

There will be 2 Mailbox servers in a DAG and 2 CAS servers. (EXCH 2010 Enterprise)
There will be about 5500 users with their database limits set to 2GB. They have a very high amount of email coming in each day. There will be about 80 databases which will be setup between the 2 servers in the DAG and none of them will go any larger than 200GB.

So I was just wondering the best setup for CPU, which I think I will go with 4 cpu's on each mailbox server, and how much memory for this to work well?
I tried the exchange calculator but I cant seem to get it to give me any info. I guess I maybe doing that wrong.
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vmich
Asked:
vmich
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3 Solutions
 
David CarrCommented:
Are you using the latest 2010 Calculator at http://gallery.technet.microsoft.com/Exchange-2010-Mailbox-Server-Role-/  ?
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vmichAuthor Commented:
Yes that is the one I downloaded but cant seem to get it to give me memory and CPU settings that I need...
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Adam BrownSr Solutions ArchitectCommented:
http://technet.microsoft.com/en-us/library/aa996719%28v=exchg.141%29.aspx explains the requirements in detail. http://technet.microsoft.com/en-us/library/dd346700%28v=exchg.141%29.aspx has memory requirements, http://technet.microsoft.com/en-us/library/dd346699%28v=exchg.141%29.aspx has CPU info.

But generally you'll be good with two to four cores and 8GB RAM if you have all the roles on each DAG member, which is the recommended method these days. 16GB is better, but you don't get much of a performance boost beyond that unless you have several thousand users on a single server. For 5500 you're probably good with 4 cores and 32GB per DAG member if you only have two. I would spread out your databases across multiple DAG members so you can utilize all your servers. You would be better off putting all roles on all servers and running an HLB between them. If you do that you can handle the load very well and have fantastic High Availability.

Note that you'll need an External Hardware Load Balancer if you do that, since you can't have Network Load Balancing and Cluster Services on the same system.
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vmichAuthor Commented:
Well we are going with 2 mailbox servers and 2 CAS servers.
So I figured 4 cpu and 40GB on the mailbox servers.
Should I put the same on the CAS servers or can they be less since the mailbox roles will be on the other 2 server?
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David CarrCommented:
The CAS servers can have less RAM. I would keep the CPU's the same. Any reason you are not doing multi-role (CAS + MB) servers?
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vmichAuthor Commented:
Well it was just how they wanted it setup...
This should not be an issue setup this way correct?
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Adam BrownSr Solutions ArchitectCommented:
CAS only won't need more than 8gb. It is fine to have cas/hub on two servers and mbx separated. Also, going beyond 32gb for exchange 2010 is a bit much even for multirole servers. Exchange will use everything you throw at it, but performance gains after 32gb are close to nil.
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vmichAuthor Commented:
Ok thanks that's why I decided to go with 24GB on the mailbox servers and 8GB on the CAS...
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vmichAuthor Commented:
I am going to have 4 mailbox server now with 24GB and 4 cores..
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Simon Butler (Sembee)ConsultantCommented:
I would dump the separate CAS role servers, and have all multi-role servers. That way you can spread the databases out. I haven't done a design with separate CAS role servers for well over two years.
In my experience the only people who want separate CAS are those who want to use WNLB. The Exchange product team don't recommend WNLB for Exchange, so if you want to do HA, don't buy the additional licences, but a proper load balancer instead.

Simon.
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vmichAuthor Commented:
Sembee,
Well the config is going to be 4 mailbox servers and 2 CAS servers..
Does Microsoft frown on this setup if we don't want to use a Load balancer?
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vmichAuthor Commented:
Sembee,
What if I  or can I use the CAS servers as mailbox also by installing the mailbox role on them since they already have the CAS and Hub?
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David CarrCommented:
Multi-role is CAS+HT+Mailbox roles all on same server. There is nothing wrong with doing that. also a hardware Load Balancer is recommended for Exchange Server 2010 but not required.
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vmichAuthor Commented:
David what I am asking is right now I have 2 mailbox servers and 2 CAS servers. Can I take the 2 CAS servers and add the mailbox role to them making 4 total servers with all of the roles and if so does that keep all of my CAS setting in tact?
Then I would add the CAS and Hub roles also to the 2 existing mailbox servers if that is correct also?
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vmichAuthor Commented:
another note to that is I guess if I can add the mailbox role to the 2 already running CAS servers, if that is possible,then I don't really need to add the CAS and HUb to the other 2 existing mailbox servers?
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Simon Butler (Sembee)ConsultantCommented:
You can add the role to an existing server if you wish.
However my preference is to have all three roles on all servers. I see no reason to split the roles out. I work with some very large clients (100,000 plus) and the best practise is pretty simple:

- all roles on all servers
- keep everything as vanilla as possible
- install everything in the defaults (move the logs and databases)
- make all changes globally - so do not have different configurations on different servers.
- use hardware load balancers.

Microsoft Exchange team don't recommend WINDOWS NLB, not load balancers in general.
http://www.stevieg.org/2010/11/exchange-team-no-longer-recommend-windows-nlb-for-client-access-server-load-balancing/

Simon.
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vmichAuthor Commented:
Simon or whomever would lie to respond,

This is what my plan was for the 4 servers I have already in place now. Let me know if this will work or not?
2 CAS which have the Hub already on them, just add the Mailbox role to them
2 Mailbox servers, just add the CAS and Hub to them.
That would give me 4 servers with all of the roles...
Is this possible to do?
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Simon Butler (Sembee)ConsultantCommented:
That would work fine - you can then spread the mailboxes over the servers.
Do ensure that that you deploy an RPC CAS Array right at the start, so if you do decide to deploy load balancers later it is easy to deploy.

Simon.
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vmichAuthor Commented:
Simon,
One more question and then I promise I will close this..
Can I just run with the 2 CAS servers and not have to worry about making the other 2 mailbox servers CAS and can I do this during production, adding these role, without affecting the users??
Sorry that was 2 questions.. :)
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Adam BrownSr Solutions ArchitectCommented:
Exchange fuctions differently when cas and mailbox roles are together, so if you have cas and mbx on the same server in part of your environmemt it is best to do it in all the environment. Also, i would schedule downtime for that change. Adding roles may require reboots and could mpact your users.
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vmichAuthor Commented:
No I don't if you look at my notes from above..
I have 2 Mailbox servers and 2 CAS with Hub servers..
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Simon Butler (Sembee)ConsultantCommented:
@  acbrown2010
"Exchange fuctions differently when cas and mailbox roles are together"

Really? What changes? I have never seen any differences. Exchange is specifically designed to not care whether the roles are on the same server or not. The only thing that having all of the roles on the same server does is stop you from using WNLB, which is no bad thing.

Simon.
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vmichAuthor Commented:
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