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  • Migration from 2003 to 2008R2

    I've got a couple of questions that I haven't seen answered

    Right now we're at 2003/2003 interim (domain/forest) functional levels are are using Exchange 2003. When we upgrade our DCs to 2008R2, we'd like to raise those functional levels. Does anyone know if that'll cause any problems with our version Exchange?

    We're also planning to move one DC off-site (to our DR facility). Not being a big expert on the networking side of AD, how do I make it available to clients at HQ? I mean, once the DC is moved to the DR, it'll be on a different network (192.x.x.x instead of 10.x.x.x). How can I ensure HQ clients will authenticate to it and not just the DC at HQ?

    Once that's working, we'll have on DC at HQ and one at DR. They'll be servicing about 1000 clients. What kind of bandwidth should I expect over that connection to DR?

    Thanks.

  • #2
    Re: Migration from 2003 to 2008R2

    Exchange 2003 will quite happily run with 2008/R2 DCs. So long as Exchange itself is not installed on a 2003 DC/GC there is no issue with raising the functional levels, and even if it is you can raise the level to Windows Server 2003 as you clearly will not have any NT4 DCs.

    You'll need to create a new AD site for the DR site. Sites define a relationship between a subnet and a geographic location so you can have Site A (HQ) associated with the 10.x.x.x subnet and Site B (DR) associated to the 192.168.x.x subnet. So long as you have these defined and a site-to-site VPN configured your clients should fallback to the DR site if there are no available DCs in their own site.

    AD replication won't take up vast quantities of bandwidth, and you can set this for out of business hours if necessary. I wouldn't bother, even over 2mb ADSL you won't notice the difference. That'll change drastically if your head office DC goes down though, I think for 1000 clients you should be looking at keeping at least 2 DCs in HQ. There's no simple answer to bandwidth without knowing more about your business requirements, acceptable downtime etc. Basically get the best you can afford, a leased line if possible and necessary for business needs.
    BSc, MCSA: Server 2008, MCSE, MCSA: Messaging, MCTS
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    • #3
      Re: Migration from 2003 to 2008R2

      Thanks for the info. You talk about falling-back to the DR box. But what if I wanted it to regularly handle half-ish of the authentication requests? Are other sites deprecated in AD or will it possibly just be picked like it is now (we've got two DCs at HQ today)? What if I wanted to increase its weight?

      Thanks.

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      • #4
        Re: Migration from 2003 to 2008R2

        Any thoughts on making the DC at DR handle as much authentication load as the HQ DC?

        What would happen if I setup the DR subnet as a subnet at the HQ site? Would all broadcast traffic travel there? That's probably not good.

        Thanks.

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        • #5
          Re: Migration from 2003 to 2008R2

          AFAIK all AD clients will default to using DCs in their own site, using SRV records in DNS. You can make the DR site part of the same site, but you would need some sort of VPN bridge to do it, which is likely to be unreliable and have vast amounts of unneccessary traffic crossing the bridge between (physical) sites as opposed to normal replication traffic crossing a site-to-site VPN.

          I would still suggest 2 DCs in HQ, with another at the DR site configured as a sperate AD site, as the best solution.
          BSc, MCSA: Server 2008, MCSE, MCSA: Messaging, MCTS
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