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New Exchange 2003 Server for Fail-Over/Disaster Recovery

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  • New Exchange 2003 Server for Fail-Over/Disaster Recovery

    I need to create a secondary Exchange server at an off-site disaster recovery location. While the primary purpose is to use this for D.R., we would also like to use it as a fail-over server.

    Ideally, the fail-over should take a minimum amount of time -- figuratively speaking, "at the flip of switch" -- without having to restore anything from our tape backup. It does not have to be automatic. If somebody has to make a few configuration changes and/or start some services, that is not a problem.

    While researching this, I've come across "Recovering a Failed Exchange 2003 Server Using the Disaster Recovery Switch" , which seems like an easy way to create a new Exchange server with the configuration as our current one. I used the method described in that article a few weeks ago to restore our production Exchange server, after the system volume was destroyed by a RAID controller failure. It worked great, but did require a re-installation of the operating system, and a restore of the mailbox stores from tape.

    1. Are there any downsides to using the Disaster Recovery Switch method to create a separate disaster recovery server? It seems too good to be true.
    • Duplicate of name in Exchange System Manager --> Administrative Groups
    • Either name of machine in the operating system or in DNS would have to be changed for fail-over

    2. How can configuration changes to our production Exchange server be replicated to the disaster recovery server?
    • I'm thinking of things like patches, hotfixes, registry changes, policies, etc., but I'm sure there are things I haven't thought of yet.
    • From what else I've read on this site, 3rd party solutions like DoubleTake are preferred, but our budget may not allow for that.
    • The mail stores and log files are stored on a SAN, and the replication of those to the disaster recovery site will probably be handled by the SAN administrator. At this point, we're planning on replication once a day.
    • Or is this even necessary, if the mailbox stores and log files on external storage are already being replicated to the D.R. site?

    Any pointers to more relevant documentation, or personal stories about experience with this type of situation, would be most appreciated.

    Thank you.

    Here is some details about our setup:
    server name: EX2K3
    server OS: Windows 2003 Standard
    application: Exchange 2003 Enterprise
    server hardware: HP DL380
    database and log storage: SAN
    external mail connectors: unix server ("MAILHOST")

    SAN +---+ EX2K3 <----> MAILHOST (unix) <----> internet

    off-site server name: EX2K3DR
    server OS: Windows 2003 Standard (already installed)
    application: Exchange 2003 Enterprise (not yet installed)
    server hardware: Sun Sunfire X4200
    database and log storage: external iSCSI

    For the time being, EX2K3DR is a member of our production domain, using our production domain controllers. While this won't work for disaster recovery (since it's assumed that the domain controllers and routing group members will also be lost), it shouldn't be a problem for a fail-over scenario. Should it? We have not created a separate Active Directory at the D.R. site.


    "Exchange replication for DR site on the cheap?"

    "Exchange Replica"

    "Deploying Exchange Server 2003 in a Cluster"
    (I'm reading this right now, to see if it's applicable for us)

    "Recovering a Failed Exchange 2003 Server Using the Disaster Recovery Switch"

    "Microsoft Exchange Server 2003 Disaster Recovery Operations Guide"

    "Disaster Recovery (Utopia, Utopia, Where art thou?)"

    "Disaster Recovery for Exchange Server in 30 minutes!"

    "Secondary Exchange in existing domain."

    "Exchange High Availability (Clustering)"

  • #2
    Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

    Move to Exchange 2007 or start looking into third party solutions.
    Exchange 2003 can't do this on its own.


    • #3
      Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

      When you look into 3rd party software, I would strongly recommend you go with NSI DoubleTake. We currently have an exchange 2k3 server offsite and use doubletake to replicate realtime changes to the target server. It not only works well with exchange, but sql databases, and file servers. Domain controllers are another story. They are currently working on a new version to failback a domain controller. Right now, if you failover a DC, you can't fail back beause of DNS issues. The only thing you need to watch out for when using doubletake, is that your servers in your production environment and your servers in your offsite location have to be on the same subnet for failover. So in other words, if your production network is a class c 192.168.1.x network, your offsite location has to be 192.168.1.x, otherwise doubletake cant failover a server thats on a different subnet. We ran into this problem in our location as we had our DR site on a different subnet and it wouldnt work.


      • #4
        Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

        Echo what Jamie said, with the addition that DoubleTake actually can work across subnets. We have it working across a VPN to a colo site for one of our customers who requires DR. Bear in mind though that this is NOT a DoubleTake recommended configuration and they give us hassle about it when we require support. A secondary issue of the VPN is that it is occasionally unstable due to the vagaries of the WAN link.

        DoubleTake is expensive, but if your requirements are for high availability and quick restore in event of a disaster then the price quickly becomes justified. As has been discussed in several threads recently this type of setup can be done cheaply, or done to work quickly, and not both. Exchange 2007 does provide far more options for this sort of scenario.
        BSc, MCSA: Server 2008, MCSE, MCSA: Messaging, MCTS
        Cruachan's Blog


        • #5
          Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

          We have a site to site VPN set up for our DR servers and its not recommended by double take - so yes they do give you hassle about that. They recommend you have a dedicated link between the 2 sitse, such as an MPLS connection or of the like - but for us, the only time we had to push data to the DR servers was the initial replication which we actually did onsite before taking the servers offsite. So the realtime data push isnt all that much so for us the site to site vpn solution was the least expensive way to go. DoubleTake emails me when the link goes down saying a failover condition has taken place. ALthough this is not a true problem, its because the local internet in the remote office tends to drop, therefore the vpn connection gets dropped and doubletake complains. it doesnt happen often though. So depending on how critical your DR plan is - if its important not to have any drop outs, then a dedicated link between 2 sites might be your best shot , but if you can get a way with doing a site to site vpn, that will work too..

          Doubletake isnt hard to set up, in fact its quite simple. There's a lot of tweaking you can do with doubletake but a lot of that isnt really needed unless required. DoubleTake tech support are really good and will help you big time. So if you do go with this product, along with the licesning, you get 24x7 tech support. When we first deployed DT, i called them contantly for help . But in the end, after its all set up , it works flawlessly.


          • #6
            Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

            Thank you all for the info. Based on this, and everything else I've read, it looks like I'll have to use third-party software to have the disaster recovery Exchange 2003 server (EX2K3DR) constantly updated with the settings from the production Exchange 2003 server (EX2K3).

            However, I'm still wondering about first part of my question, regarding the initial setup of the disaster recovery server.

            Is there any downside to installing Exchange 2003 on it using the disaster recovery switch, as described in "Recovering a Failed Exchange 2003 Server Using the Disaster Recovery Switch"?
            :\Setup\I386\Setup.exe /DisasterRecovery
            As mentioned earlier, I actually used this method to restore our production server a few weeks ago. It worked so well, I'm very tempted to use it to use it for our new D.R. server.

            But I'm concerned about any unforeseen and unintended behavior if I use this to add a new D.R. server to our environment.

            I guess I'm either over-cautious or over-paranoid, I can imagine all sorts of horrible things happening (e.g., mail starts being routed to the new disaster recovery Exchange server).

            The D.R. Exchange server is part of our production Windows domain, but on a separate sub-net connected via VPN to the disaster recovery site across town.

            SAN (fiber) +--+ EX2K3 (routable class C I.P.) --------{ VPN }-------- EX2K3DR (private I.P.) +--+ D.R.-SAN (iSCSI)

            We do not have a separate Active Directory for the disaster recovery site, nor any domain controllers installed there yet.


            • #7
              Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

              If you are using third party software to do the data replication then you setup the server as per their instructions. Almost certainly it will not involve DR installation because you cannot have two machines with the same name on the same network.

              Simon Butler
              Exchange MVP

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              • #8
                Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

                Almost certainly it will not involve DR installation because you cannot have two machines with the same name on the same network.
                Do you mean the name of the Windows server, or the name of the Exchange virtual server?

                If the former, the two machine names are different: EX2K3 (production) and EX2K3DR (disaster recovery).

                If the latter, can the name of the virtual server be changed in Exchange System Manager?


                • #9
                  Re: New Exchange 2003 Server for Fail-Over/Disaster Recovery

                  After reading through some more documentation, I believe the proper terminology for what I want is a Standby Recovery Server (unless we budget for some application like DoubleTake to build a fail-over server).

                  reference: "Exchange Server 2003: Member Server Recovery Methods"

                  Using an Exchange Standby Recovery Server
                  . . . . .
                  Install your Windows Server 2003 operating system to a workgroup, including both the SMTP and Network News Transfer Protocol (NNTP) IIS components as part of your installation. Additionally, configure the same drive letter and drive space configurations as the server that is running Exchange and that you intend to replace.
                  So what I need to do is remove the current disaster recovery server, EX2K3DR, from the domain, and then install Exchange 2003 on it.

                  Since the plan is to have a current copy of the database and transaction logs available at the D.R. site via SAN replication, I should be able to mount the mailboxes at the D.R. site in the event of a disaster or server failure.

                  After that, route mail through the D.R. Exchange server (still have to figure that part out).
                  Last edited by Robert R.; 24th February 2009, 20:29.