Exchange 2010 High Availability (a bit of advice pls)

I am currently designing and installing a new network for my employer and could do with a little advice regarding Exchange.  The company consists of 2 branches, North and South.  I am initially dealing with the South branch, and after I've completed, implemented and tested the South network for a while I'll do the exact same design in the North branch.

The South network currently consists of x2 Hyper-V hosts with a failover cluster:

HyperV 1                                           HyperV 2
VM: DC1                                              VM: DC2
VM: SRV1 ------ failover cluster ------ VM: SRV1

SRV1 is a VPN server, a File Server (DFS) and a DHCP server.  We are tyring to create a fully resilient network.

Regarding Exchange... we have approx 20 mailboxes at each branch, and I had a few ideas:

   1) ALL Exchange Roles onto 1 VM on HyperV 1, then the same on HyperV 2 with a CAS Array and DAG between the 2 VMs

   2) 1 VM within the failover cluster with ALL ROLES installed on it

   3) Seperate the roles as follows:

HyperV1                                                             HyperV2
VM: EX1 (Hub & CAS)    ----- CAS array -----    VM: EX2 (Hub & CAS)
VM: EX3 (MBX Role)       -----      DAG     -----    VM: EX4 (MBX Role)

I am trying not to do Option 3 because of the increased number of VMs required (administration), it seems a bit messy.

When both networks are implemented, I am hoping to have a company-wide exchange setup.  So if I could implement Option 2, then the North and South exchange VMs could replicate / share exchange info (provide resilience).

Any comments / suggestions???

Cheers, Andy
andrewprouseAsked:
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AkhaterCommented:
well option 3 is the best one since it will provide you with full HA and redundancy

option 1 will give you Redundancy but not HA any failover will be manual (Second best)

option 2 will not give you redundancy at all, if exchagne is down exchange is down

I would advise you to go for 1 or 3 depending on your budget.

1 is pretty good, probably the best money/availability option

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andrewprouseAuthor Commented:
Thanks Akhater, option 1 it is then.  Everything I read seems to suggest that the Exchange roles are separated, am I okay to combine them in my production environment (20 mailboxes per site)?

Also, if I create a CAS array and DAG between the 2 South Exchange VMs, is there a way to join the North branch Exchange VMs to create one exchange 'organisation' ?  How would I configure this, one DAG per site, or one DAG for the entire company?  Also, how about the CAS array?

Cheers, Andy
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AkhaterCommented:
you are more than fine to combining them for 20 users, the only issue is the lack of HA your system will not failover automatically

yes you can have one exchange organization for south and north

I suggest you create 2 separate DAGs, one for each, unless you have a very good and reliable bandwidth between the two

for the CAS arrays it has to be one per site
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andrewprouseAuthor Commented:
When you say 'lack of HA', surely I have HA with the fact that I'll have 2 CAS, HUB & MBX servers per branch. Therefore 2 copies of the database, 2 servers for the clients to talk to and 2 frontend servers per site.

Will this not provide resilience (HA)?
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AkhaterCommented:
When all roles coexist in a DAG

1. Your mailboxes are on 2 servers so you do have redundancy
2. You have 2 CAS servers so you have redundancy

however the thing is that, in that case, you cannot provide windows NLB to your CAS servers since NLB and Clusterign cannot be done simultaneously

so you can

1. get a hardware NLB and solve all your issues
2. use DNS round robin for you CAS server, this will provide you with redundancy and load balancing on the cas level however when a server fails 50% of your clients will be disconnected and you need to manually edit the dns for this to work
3. point your cas array name to the DAG IP. this will provide you with HA and redundancy however not with Load Balancing snce all clients will be connected to one of the 2 cas servers


I hope it makes more sense
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SteveIT ManagerCommented:
Have you considered going hosted ?

This would ensure high availability, resilience as well as provide scalability based on the Exchange 2010 configuration.
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andrewprouseAuthor Commented:
Akhater

Thanks for the advice, just one more question though.

When you say that NLB is not supported within clustering, shouldn't I be okay as long as I ensure that the Exchange VMs aren't clustered resources (just normal VMs) ??

sgsm81

What do you mean by 'hosted' ??  As in externally hosted?
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AkhaterCommented:
No I am not talking about the hyperV part, you got that perfectly correct

You have mailbox role that need dAG clustering and CAS roles that need NLB on the same machine
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andrewprouseAuthor Commented:
So the issue with installing all roles on one VM is that a DAG group and NLB for the CAS array can't co-exist.  So I guess I'm back to OPTION 3.

Seems a bit messy, especially as we have 2 sites (means a total of 8 exchange servers).

Many thanks for all of your help.  

Much appreciated.

:-)
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andrewprouseAuthor Commented:
Akhater - Not sure if you're still there..hope you are...

I had one final idea (trying to cut down the number of exchange server - save admin headaches and costly licences).

Could I install all exchange roles onto a HA VM (a VM within a failover cluster).

No DAG required, no CAS array required, just one HA server (per site) serving clients.

If this is possible, is there still a way to somehow sync / replicate exchange data with the other branch??

Cheers, Andy
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SteveIT ManagerCommented:
Hi

Yes externally hosted exchange as a viable alternative and removes a lot of headaches
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