Thursday, January 21, 2010

Exchange 2010 - High Availability and Disaster Recovery With Only 3 Servers - Part 1

Background

One of my customers wants to know how to leverage Exchange 2010 to provide high-availability (server failure) and disaster recovery (site failure) using the minimum number of servers. Here is a walk-through of the reference design and server fail-over experience:

Production Site:
  • DC (FSW)
  • Hardware Load Balancer (VIP for CAS Array)
  • EX2010-1 (CAS/HTS/MBX Roles)
  • EX2010-2 (CAS/HTS/MBX Roles)

DR Site:
  • DC-DR (Alternate FSW)
  • EX2010-3 (CAS/HTS/MBX Roles)

Configuring High Availability with two Exchange 2010 Servers

I am going to assume that you are already familiar with the process of installing Exchange, creating a DAG, and creating a CAS Array - so here is an overview of the configuration:

All three servers are added to my DAG and I set the Domain Controller as the File Share Witness (note: since there are three servers in my DAG, it will use a Node Majority under normal circumstances).


Next I configured my database to replicate to all of the members of my DAG.


Next I created a Client Access Array in the Exchange Management Shell and assigned it to my database.


Next I created a VIP on my hardware load balancer. I used a Barracuda 340 - but really any HLB should be fine.


Next, I created DNS records for the VIP on my hardware load balancer. I used two addresses: internal.test.local and external.test.local

Finally I configured the InternalURL and ExternalURL on my Exchange Virtual Directories to point to my VIP.

What happens during a Server Failure

At this point I now have high availability within my production site that can tolerate the failure of either EX2010-1 or EX2010-2.

At this point, DB1 is mounted on EX2010-1. When I look at my Connection Status in Outlook, it shows that I am connected to the VIP (in this instance, I am actually connected to EX2010-1 via the load balancer).


If I decide to do a graceful fail-over my database to EX2010-2, my Outlook Clients will receive a notification that they will need to restart Outlook. Note that even after the fail-over I am still using EX2010-1 as my RPC Client Access Server via my hardware load balancer.



If I decide to do a fail-over of my RPC Client Access Server from EX2010-1 to EX2010-2 (via marking EX2010-1 down on my hardware load balancer), my Outlook client will briefly lose connection before it is able to successfully reconnect.



In the event that I had a non-graceful server failure, my Outlook client would briefly lose connection before reconnecting (and possibly prompting my to restart Outlook).

3 comments:

  1. Couple days ago I was at the Inet and saw there many different things, but one of them interested me more than anything. It was one software which might aid in any situation related to ms exchange server not worse than had assisted me before - recover stm files.

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  2. Wonderful blog & nice content.Its really helpful for me, awaiting for more new post. Keep Blogging!!!

    Business Continuity UK

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  3. Good article, it provides the information related to exchange disaster recovery, i used the automated tool ( http://www.lepide.com/exchange-manager/ ) which recovers corrupt Exchange database as well as restores selected mailboxes from backup and transfer mails to them from PST, OST, EDB or Live Exchange Server. This tool converts any size edb files to new/existing pst files and support all version of exchange server. It provides the facilitate to export mailbox including all items like inbox, sent items, outbox, task, notes, appointment etc. to outlook pst files .

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