Adding second domain controller to Windows 2008

Hi,
I am in the process of adding a second domain controller to Windows server 2008 Enterprise.
On the first Domain controller I am running Exchange 2010.  
The first domain controller is also a global catalog server.

Please see attached screen shot.
My questions:
1. Why would I want to make this second domain controller, read only?
2. By default "Global Catalog server" is checked. Do I want to have this second domain controller be a GC server as well as the first? From what I understand, you can/should only have one GC server.
3. Should I also install a DNS server on this second DC? Is that a good idea in terms of redundancy or is it not necessary?
Thanks,

Mike

Screen-shot-2011-03-21-at-10.07..png
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nachtmskAsked:
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Glen KnightConnect With a Mentor Commented:
There is no reason why you wouldn't have all DC's in a single domain forest as Global Catalog servers.

You would normally use Read-Only domain controllers in branch offices or where physical security is an issue.

It would be a good idea to install DNS on the second DC if you only have one DNS server as this will allow clients to find/authenticate resources should the first server be unavailable for any reason.
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Brian PiercePhotographerCommented:
I would accept the defaulr nad have your second DC both a global catalog and DNS server - there is nothing to be lost and a lot to be gained in terms of redundancy and resilliance.

There is no point in making it a RODC though - this is designed for remote/insecure sites.
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sunnyc7Connect With a Mentor Commented:
1. Why would I want to make this second domain controller, read only?
>> You shouldnt for an exchange environment. Exchange wont work with a RODC as it updates the schema during installation / installation of SP's / updates etc.
As demazter said, this can work for auth in a branch office / hub-spoke scenario.

2. By default "Global Catalog server" is checked. Do I want to have this second domain controller be a GC server as well as the first? From what I understand, you can/should only have one GC server.
>> You can have more than one GC.

3. Should I also install a DNS server on this second DC? Is that a good idea in terms of redundancy or is it not necessary?
>> Recommended to have 2 DNS servers atleast for redundancy.
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Mike KlineCommented:
Where did you read that you should only have one GC.  Try to make every DC a GC.  See bullet one here:  

http://adisfun.blogspot.com/2009/04/lessons-learned-from-eric-fleischman.html

No one can really challenge Eric F :)

demazter nailed it as usual.

Thanks

Mike
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nachtmskAuthor Commented:
Thanks for getting back on this so fast.
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Sigurdur HaraldssonSystem AdministratorCommented:
Your questions:
1. Why would I want to make this second domain controller, read only?
2. By default "Global Catalog server" is checked. Do I want to have this second domain controller be a GC server as well as the first? From what I understand, you can/should only have one GC server.
3. Should I also install a DNS server on this second DC? Is that a good idea in terms of redundancy or is it not necessary?

My answers:

1. Why are you adding the second DC and where are you placing it? Second DCs are usually for redundancy and load balancing. If it is not a question of physical security in a branch office, then there is no reason to make it a RODC.

2. Microsoft recommends that all DCs in a domain should be Global Catalogue servers except when the DC hosts the Infrastructure Master role. However, in most cases, all DCs are GCs.

"The Infrastructure Master (IM) role should be held by a domain controller that is not a Global Catalog server (GC). If the Infrastructure Master runs on a Global Catalog server it will stop updating object information because it does not contain any references to objects that it does not hold" - http://www.petri.co.il/understanding_fsmo_roles_in_ad.htm

3. Make the second DC a DNS and use Active-Directory integrated DNS. That way you have full redundancy as both DNS servers hold writeable zones. Otherwise, you will have to recreate your DNS zones if the server holding the primary zone fails.

So the short version of the answers is:

1. You wouldn't.
2. Yes. You can and should have many Global Catalogue servers.
3. Yes and yes.
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Sigurdur HaraldssonSystem AdministratorCommented:
LOL, you closed it as I was answering :-)
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Glen KnightCommented:
The GC/IM placement only becomes an issue in multiple domain forests.

Have a look at a great article from tigermatt here, which explains the FSMO roles: http://www.experts-exchange.com/Software/Server_Software/File_Servers/Active_Directory/A_2796-Demystifying-the-Active-Directory-FSMO-Roles.html
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nachtmskAuthor Commented:
Thanks sighar. Your answer was very complete. I'm sorry but I already assigned points before your answer came in.
I'll likely have more questions though as I move along in this process.

Thank again.

Mike
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