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Exchange 2007 to 2010 High Availability considerations

Posted on 2012-09-17
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Last Modified: 2012-09-19
We are looking to upgrade to exchange 2010 sometime in the near future. We are currently running exchange 2007 in a CCR configuration as detailed below.

Approximately 1600 mailboxes
2 - HUB/CAS servers NLB
2 - Mailbox servers CCR

I have just started reading about all of the HA options available in exchange 2010 and have a few questions. We are looking to size this exchange installation for about 2500 users. So far the possible configurations I have thought about are either

3 server DAG each server having the following roles MBX+CAS+HUB. This configuration would require a hardware load balancer (prob 2 for some HA/failover).

or

3 server DAG mailbox role and 3 other servers running HUB/CAS array. This configuration could use MS NLB for the CAS array but most likely would also use 2 hardware load balancers.

Now I am quite new to exchange 2010 so I am looking for any possible flaws in my logic with these designs. Im not sure whether we would go completely virtual using VMware, purely physical, or some combination of virtual/physical.

The first solution with 3 servers and all roles seems like it would require less hardware and effort to setup since the builds would be identical but are there any issues that i am not aware of.

Thanks
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Question by:Joseph Daly
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by:Larry Larmeu
Larry Larmeu earned 668 total points
ID: 38406850
Important things to note are one that you pointed out, that if you combine DAG mailbox servers and NLB you will be required to use a hardware load balancer.  Another important thing to remember is that if you combine the roles you will need to scale your VMs accordingly.

Have you run the Exchange Mailbox Server role requirements spreadsheet?  It's a helpful tool to gauge how to spec out your environment:

http://gallery.technet.microsoft.com/Exchange-2010-Mailbox-Server-Role-/

I personally perfer to split out them into Mailbox + Cas/HUB roles when dealing with NLB/DAG environments, but it is definitely supported to go either way and given your number of mailboxes you should be able to support combined roles without having to have a ridiculous VM with like 8 CPUs and 64GB.
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by:Joseph Daly
ID: 38406928
From what Ive read MS highly recommends a hardware load balancer so I think that whatever implementation we end up going with we will be using 2x hardware load balancers.  

With that in mind the only other real difference that I am seeing is that the first implementation with all 3 roles per server would require less servers (3) but more resources CPU and MEM.

The second option would require more servers (6) but would give us the leverage to tailor the hardware specifically toward each role.

Would it be possible to configure a 2x Mailbox DAG and a 3x CAS array? Right now it seems like our 2x CAS array struggles when hit with a lot of mail at once.
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by:Joseph Daly
ID: 38406930
Also as far as the exchange calculator I downloaded that earlier today and tried running through it but some of the fields were pretty confusing and the numbers I got were extremely large.
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by:Larry Larmeu
ID: 38406940
Yes you could do 2x mailbox and 3x CAS.

It's certainly advisable to use hardware load balancers if that is an option for you.
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by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 1332 total points
ID: 38406968
That number of users there is only one design I would be considering.

2x DAG (possibly three, depends on what the spreadsheet says).
2x CAS
HW Load balancer.

All would be in VMWARE.

Two physical machines, with one each of the roles, plus a domain controller. You need Enterprise edition of Windows for DAG, so that allows 4 VMs per physical chassis.
The HW Load balancer would also be virtual, probably a Kemp.

The Exchange product team no longer recommend the use of Windows NLB for Exchange, and therefore it isn't something I would even consider.

Simon.
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by:Joseph Daly
ID: 38409720
Looking at the exchange calculator it mentions that if you have 3 or more DAG groups the amount of backups you need to perform is minimized?

If a DAG group is just multiple copies of your data in different locations how does that minimize how much you have to back up?
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by:Joseph Daly
ID: 38409737
Am I also right that having a DAG group spread across 3 servers will allow me to spread the active databases across the 3 servers for better performance? Currently in our exchange 2007 setup the DBS are all active on the same server. With the DAG a copy of the DBs can be set active on any of the 3 servers.

So for example a 3 server DAG with 3DBs I could have each DB active on a seperate server to maximize performance?
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by:Larry Larmeu
ID: 38410695
With 3 copies Microsoft does say that the need for backups is minimized.  With the 24/7 online error correction and defrag the chances of database corruption in Exchange 2010 is much lower than in previous versions and having multiple copies allows you some extra protection of your data.  I personally still favor having backups, though.

Yes, you can have the 3 databases running active on different servers.  The DAG has a database priority order, so you just set the database priority to 1 for DB1 on server 1, 1 for DB2 on server 2, 1 to DB3 on server 3, and then set your backup copies as priority 2 and 3.
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by:Simon Butler (Sembee)
ID: 38412613
If all three of the servers are in the same physical location then it isn't a problem to spread the active databases across multiple servers. However if you are splitting them up different physical locations i wouldn't want to run A/A/A, simply becasue that caue unpredicible results in the event of a loss of the connections between the servers.

Simon.
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by:Joseph Daly
ID: 38413922
All 3 servers would be located in our main corporate office so I think an all active setup should work properly.

What have you guys seen in terms of physical vs virtual. We have a VMware 5 environment that I am sure we would want to leverage for this but im not sure if wed want to put our mailbox servers on physical servers.
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Simon Butler (Sembee) earned 1332 total points
ID: 38414512
I have done exactly five deployments on to physical this year.
The rest (over 30) have been on to virtual. There is almost no interest in using physical machines.

The most common scenario I am seeing is where two or more physical machines are used, with a number of virtual machines on them. This could be a DC, the CAS/Hub role servers, BES etc. As you have to use Enterprise edition of Windows for DAG support, this provides four VMs per physical machine licences, it makes sense to put other things on the same physical box.

Simon.
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by:Joseph Daly
ID: 38414532
Well I think this thread has given me a decent amount to think about. Thanks for all the help.
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