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Exchange HA Setup

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Exchange HA Setup - 25.Feb.2011 9:22:23 AM   
Haigy

 

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Joined: 26.Jul.2006
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Hi, I have just started looking at putting exchange 2010 into my organisation to replace our exchange 2003

I am looking to get away from my Doubletake setup and use DAG but was looking for some advice on setup

I really only want to use 2 Servers for my full setup (witness server will sit on another server), one would be in my main office and the other server at a remote site over a 10mb dedicated line, we will have users utilising outlook anywhere, owa etc and blackberry users

would I get away without putting a CAS server as a sort of front end server (I am sure that is what a CAS does, just reading up and about to start a test in my test lab)

everything will be installed on hyperv, any major gotchas on this?

thanks for any advice on this
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RE: Exchange HA Setup - 25.Feb.2011 10:35:27 AM   
de.blackman

 

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Actually CAS is nothing like a frontend. CAS is a REQUIRED role that allows communication between the client (both internal and external) and their mailbox. All connections from clients (such as Outlook, OWA users and so on) must go through the CAS. In fact, when you setup an Outlook profile, it is the CAS server name that is in the profile, not the mailbox server. The frontend server is a completely optional role and it is used by only external clients to connect to their mailboxes. It functions as a "pass-through" to the backend server.

It is a requirement for you to have at least one CAS server in each site that will contain a mailbox server. So in your design, you can definitely get away with having 2 servers, each running the required roles (mailbox, CAS and hub transport). You can configure the 2 servers in different locations to be members of the same DAG to provide HA. Are you also planning to implement site resiliency (if one site goes poof, other site takes over all connections and services)? Are you planning to have both servers running active databases?

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Ibrahim Benna - Microsoft Exchange MVP
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Navantis
@IbrahimBenna

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RE: Exchange HA Setup - 25.Feb.2011 10:55:53 AM   
Haigy

 

Posts: 11
Joined: 26.Jul.2006
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thanks for the quick reply and understand a bit more about the CAS role now, for a small organisation I think hosting all services on a server is fine

All my users are on one site, other site is just for backup, currently working on this, so I think it would be passive, but would like to fail over if my main site goes down and we had to use the other site or if my exchange fails on main site I can failover to it, would be around 2 hours behind incase of corrpution of database etc

would this work

again thank you

(in reply to de.blackman)
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RE: Exchange HA Setup - 25.Feb.2011 11:30:08 AM   
de.blackman

 

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From: Toronto, Canada
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So it sounds like you are looking for site resiliency more than high availability. If you wanted high availability then I would say to implement 2 servers running the three required roles in the main site and you have achieved HA

I assume you have an internet connection at the passive site?

DAG server failover happens within 30 seconds so your failover time is not 2 hours. Lets say your active DB gets corrupted somehow, that does not mean that your standby copy will be corrupted as well. DB corruption is usually physical and local to the server. Besides Exchange always checks the transaction log files that are copied to the passive server for corruption before it commits them into the database, thus eliminating possibility of logical corruption.

http://technet.microsoft.com/en-us/library/dd638137.aspx
http://technet.microsoft.com/en-us/library/dd638121.aspx
http://technet.microsoft.com/en-us/library/dd638104.aspx

If you do want to achieve a 2 hour delay in commiting the log files into the passive database, you will need to configure the passive copy of the database as a lag copy, this way there will be a delay or lag (ReplayLagTime) before the log files are committed.

http://technet.microsoft.com/en-us/library/dd979802.aspx
http://technet.microsoft.com/en-us/library/dd335158.aspx

Hope you like reading (empower your mind to strengthen your skills!)


_____________________________

Ibrahim Benna - Microsoft Exchange MVP
Forum Moderator
Navantis
@IbrahimBenna

(in reply to Haigy)
Post #: 4

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