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How do I set up an off-site failover set of Microsoft servers?

Posted on 2008-10-28
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Last Modified: 2012-08-13
Currently I work for a company with a single domain controller, a single file server, a single exchange server, and a single application server.  We have a remote office 200 miles away connected via MPLS.

What we want to set up is a situation where the remote office houses servers that are not used unless there is a failure of our connecting circuit.  We've come accross DFS and wondered if this would in part do what we are after.  I'm not looking for specifics for how to configure things, just validation that we are headed down the right road.

This is what I have pictured right now... tell me if I'm correct or correct me where I'm wrong please.

We can set up a second domain controller at the offsite location (this part is just standard domain controller stuff failing over to it if the other is gone, right?

We then set up a second file server that uses DFS to be a 100% duplicate of the first fileserver.  Then when the circuit is down, users at the second location will be talking to the second domain controller and it will be sending their file requests to the second fileserver.  Then when the circuit comes back up they need to sync.

Exchange will need a duplicate as well, but I don't know if the term we are after is a clustered set-up or if there is a different way to acomplish a failover with Exchange.  We have external mail coming in covered via a third party that will re-direct our MX record.  We just need users to failover to the secondary Exchange server and when the circuit comes back up for the two servers to sync.

All I'm looking for is validation or correction, like I said.  So an answer like "yes, you add a second DC to the network and add a second EX server as a cluster will do what you want"  or "no, a clustered EX server won't act as a failover, you would need the failover EX product to do that"

Thanks in advance!

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Question by:archaic0
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dfxdeimos earned 250 total points
ID: 22826350
Yes, setting up a second DC at your remote site will provide the failover capabilities that you desire.

Yes, setting up a DFS share between the two sites will give you the failover capabilities that you desire.

Probably the easiest way to set up the Exchange failover would be to simply install Exchange at the secondary site, let it sync up with your existing organization and then move all the users in the second site over to the storage group on their new local server.
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by:tigermatt
tigermatt earned 250 total points
ID: 22826392

On the Active Directory things, you would setup an Additional Domain Controller at the other site. Configure it as a Global Catalog server and tell Active Directory Sites and Services the other site and the other site's subnet. Each site would then automatically use its local DC(s) for authentication, reducing traffic on your link.

If you use DFS in each site, then workstations at each site will connect to their local DFS host to access files. This isn't a problem, but won't achieve what your original aim was; however, from experience, I would suggest you use DFS and just allow replication at all times so changes are instantly available in the other site.

Configuring an Exchange Cluster will enable you to have failover, but it needs Shared Storage, something you can't easily have running on sites 200 miles apart. What I would suggest instead is you make use of Exchange 2007's CCR, which DOESN'T require shared storage, or look at a product like DoubleTake which can do replication and failover at the touch of a button.

-tigermatt
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by:archaic0
ID: 22826442
If I follow what I've read so far about DFS I think we may have it in place already, we just aren't using multiple targets right now.  My fileserver shares have addresses like //domain/folder instead of the old //server/folder.  This is DFS, right?

If I have DFS set up and only pointed to one target, the local fileserver... then add a target for a share of a secondary fileserver... does DFS take care of replication both ways?  Or would I have to at least start by making a copy of the data from one place to the other?

We might like the idea of moving the users mailboxes to their local server, but we are primarilly thin-client so the users are coming to our site for a TS desktop so moving their mailboxes to their EX server wouldn't help us.  I didn't mention that before, sorry.

Does simply installing a second EX server and letting it sync up provide for the failover at that point of all users at both locations if one server simply dropped off?
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by:dfxdeimos
dfxdeimos earned 250 total points
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I am not experience with EX servers, so I couldn't help you there.

Yes, adding a second target for your DFS share will take care of the replication (including the initial push) but I would do it at night the first time so your network doesn't get bogged down.
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by:archaic0
ID: 22826494
I'll clarify a little with one part I didn't mention before... we're primarilly thin-client, so the rest of the picture is that day to day users at site B are using a remote desktop from site A and those terminal servers are then local to the DC and EX at site A.  In a failover situation, there will be terminal servers at site B that users will connect to (automatically upon reconnection attempts) and those terminal server at site B then would attempt to talk to the DC and EX at site A, fail, and find the site B servers online.

I hope that clears things up a little.  There really aren't any workstations at site B that would benifit from local connections to the site B DC or EX server.
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by:archaic0
ID: 22826516
So DFS even does the initial push... good, but if we wanted to, could we do a manual push?  If we determine that the data size is simply huge, say greater than 100G, then we'd much easier move that data via a hard drive and simply make the 2 hr drive versus waiting days for the sync across 1.5mb.

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by:archaic0
ID: 22826533
P.s.  I'll be bumping the points, you are both helping a lot.
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by:tigermatt
ID: 22826555

If they are logging in to Virtualised Environments in Site A, then Site A's DCs are going to be used first, and the Site B DCs, replicated Exchange Servers and DFS targets will only be used if the server(s) in Site A become unavailable for whatever reason.

I've not got experience myself with moving data on a Hard Drive for DFS purposes, then setting it to replicate. I would take a guess as to say that wouldn't work, since DFS would need to keep its own log of data which has / hasn't replicated, but I would be interested to hear from anyone who has moved this amount of data by a hard drive between sites and plugged it into DFS.

-tigermatt
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by:dfxdeimos
dfxdeimos earned 250 total points
ID: 22826563
Yes, here is an excerpt from http://technet.microsoft.com/en-us/library/cc773238.aspx

Q: Can I seed a replication group member with data prior to the initial replication?
A: Yes. DFS Replication supports copying files to a replication group member before the initial replication. This "prestaging" can dramatically reduce the amount of data replicated during the initial replication.

To prestage a replication group member, copy the files to the appropriate folder on the destination server(s), create the replication group, and then choose a primary member. Choose the member that has the most up-to-date files that you want to replicate because the primary member's content is considered "authoritative." This means that during initial replication, the primary member's files will always overwrite other versions of the files on other members of the replication group.

For more information about the initial replication, see the TechNet article about what to expect during initial replication (http://go.microsoft.com/fwlink/?LinkId=75044).
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by:dfxdeimos
ID: 22826571
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by:tigermatt
ID: 22826582

As for your other comment (didn't notice it, sorry), if you are using \\domain\sharename, then you have DFS Namespaces enabled in the domain. For the replication side of things, you use DFS-R, a separate component of DFS which specifically handles Replication. What I would suggest you do is configure the replication to replicate folders between servers at each site, then publish each share from the server as a separate DFS Target in your domain-level DFS namespace. Thus users will not be impacted (with the exception of a slight speed detriment) with their file shares; if the site A DFS root is unavailable, the \\domain\sharename namespace will failover to Site B.

Exchange is not designed to handle having mailboxes in two locations - it is mailboxes on one server and one server only. If you want a complete copy of all mailboxes in Site B, you'll need some form of replication software; again, I highly recommend DoubleTake.

-Matt
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by:tigermatt
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dfxdeimos, thanks for doing the research. It looks like you will be able to move your 100GB+ of data between the sites and then configure the DFS-R to just replicate changes :)
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by:archaic0
ID: 22826765
OK, it looks like we have DFS covered... the only thing fuzzy is Exchange.

I sounded like dfxdeimos said I could set up a second EX server and it would function like I'm after, but tigermatt mentioned shared storage...

Simply setting up a second EX server will give me two servers for load balancing maybe?  But it won't allow the second one to function as the only one if they get disconnected from each other?

Is that where we're at?

So a third party app, like DoubleTake, is required to give me a fully functional off site backup EX server?
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by:tigermatt
tigermatt earned 250 total points
ID: 22826832

Exchange is designed out-of-the-box so that mailboxes reside on one server and one server only. This means, if you didn't use thin clients, you could have site A's user mailboxes on site A's Exchange Server, and the same at Site B. They would then have local access to their data.

If you want ALL mailboxes to reside on both Exchange Servers (i.e. for high availability), you can either go the Microsoft route - a Cluster, which requires Shared Storage, or you can look at DoubleTake, which will handle and monitor the replication, and do automatic failover if either Exchange server is unavailable, as necessary.

-tigermatt
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by:archaic0
ID: 22826907
Well we're not opposed to third party solutions, but we might have something in the way of shared storage but what does that mean exactly?  A single place that both locations can see?

We have two SANs, one local and one remote.  Specifically for off-site replication of backup data and the like.  It only replicates once a day however, and is a manual process for data to be live at the off-site location.

For the doubletake solution, does this work with things such as BES (Blackberry server).
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by:tigermatt
tigermatt earned 250 total points
ID: 22826950

When I say Shared Storage I do mean something like a SAN. Ideally when you set up a cluster you want to have the nodes in the same location as the SAN; trying to start doing replication of the Exchange databases, or have Exchange remotely connect to a SAN, would be a nasty recipe for disaster.

There is Exchange 2007's CCR (Continuous Cluster Replication) which acts like a cluster, but doesn't need any shared storage, that is something you could keep in mind. http://technet.microsoft.com/en-us/library/bb124521.aspx

And DoubleTake should work with BES but since I'd check before committing yourself, I can't see any reason why not though.

-Matt
-tigermatt
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by:archaic0
ID: 22827027
Well depending on the pricing for DoubleTake versus our calendar free time we were looking to move to EX 07 anyway after we got our off-site project completed... but migrating sooner sounds like it will make the off-site project easier so we may switch the cart and horse on that one.

Thank you two for your help.  You've really cleared up our initial concerns.  Now we move into the testing and validating phase.

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by:tigermatt
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You're welcome, thanks for the points :)
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