How do I failover to my DR Site.

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osiexchange

What is the proper way to activate a database in a DR site using a Exchange 2010 DAG? Here is my setup. I have two mailbox servers in my production site and one mailbox server with the CAS and Hub Transport role in my DR site. Each Each server in the production site has 3 databases which replicate to the other server in production. One of the 3 databases in production also replicates to my DR server. This is the database my mailbox is on for testing. What I did was shut down my two production servers and then tried to activate the copy on the DR server. I am doing this by right clicking the database in the EMC and selecting Activate Database Copy....No matter what I try, it fails because it cannot connect to the production server. But, in a real DR situation, these servers will probably be down so how do I activate this database in my DR site so users can access it. This is the last hurdle I have before I move this into production so I am hoping someone can help me out.
 
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Ed Crowley [MVP]

When two of three nodes are down, you don't have a quorum. Yes, there is still a quorum. Elan Shudnow's blog posts help explain what you need to do, depending on whether you are running in Database Activation Coordination (DAC) mode.

http://www.shudnow.net/2010/06/30/exchange-2010-database-activation-coordination-dac/

That article points to this one, which is more directly related to what I think is your problem.

http://technet.microsoft.com/en-us/library/dd351049.aspx

Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."
 
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osiexchange

I am even more confused now. I have 3 nodes in my DAG. Two in the local datacenter and one in the DR site. My primary datacenter has a FSW. I would think I would need this since if one of the nodes goes down, I still have quorum in my primary site. But, If both my nodes in the primary site go down, as in a disaster, how would I ever bring up my node in the DR site since I would not be able to achieve quorum with just one node?
 
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Ed Crowley [MVP]

One node in the DR site out of three is not a majority. Even adding a witness in the DR site gives you only two out of four. Did you read the articles I posted?Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."
 
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osiexchange

Yes. It's sounding like a need two nodes in my DR site for this to work. This was my thought but I just wanted to verify. This means another deployment and another license.
 
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Ed Crowley [MVP]

You can have the node plus a FSW.Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."
 
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osiexchange

OK, to get this straight. With 3 nodes and a FSW, I can still have quorum if I lose two nodes? Your previous post seems to indicate this is not possible. So what do you mean by " You can have the node plus a FSW" ? I can easily tear down my Exchange Enterprise in my DR site and build out two Standard Editions if I need to. My current configuration of 3 nodes and a FSW does not qualify for failover if I am understanding you correctly. If I must have four nodes and a FSW, I can do that.

It seems to me you should be able to do this with 3 nodes and a FSW but I am unclear.
 
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Brian Day MCITP

Remember, odd-numbered DAGs do not use a FSW because there is no tie to break.

There is no way to automate failover with only 2 datacenters if the datacenter with the majority of votes in the DAG is lost. You will have to perform manual datacenter switchover if that happens. You can read up on datacenter switchovers here;

http://technet.microsoft.com/en-us/library/dd351049.aspx

Some customers are putting an even number of DAG nodes in both datacenters, and their FSW in a third datacenter. I have to strongly enforce the need to have a fully mesh network topology between all 3 sites before contemplating doing this. This means tracking down every single copper/fiber and making sure no 2 paths between datacenters cross at any point. If some backhoe were to dig up a piece of fiber that connects the primary site to both the DR and FSW site then you're primary site would dismount all DBs.

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
 
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osiexchange

I have an odd-numbered DAG with 3. What happens if I lose a node in my primary datacenter which has two nodes and my node in the DR site is not reachable. Will my single node in the primary datacenter stay up? I thought I needed a FSW in my primary for this reason.

For my current situation, I have two nodes in the primary datacenter along with a FSW. I have a single node in my DR site. If I lose both my nodes in the primary site, I need to be able to activate the databases on my DR server. Is this possible with only 3 nodes and no FSW?
 
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Brian Day MCITP

Your first scenario means 1/3 votes will be online, so no quorum majority, so all DBs will dismount automatically.

Your current situation does not have a FSW in use. You configured a FSW when the DAG was created because it is a required attribute, but since you have 3 nodes in the DAG it is not being used. To be able to activate the DR site if the primary site goes down, follow the steps in the article I provided.

If you did have a total of 4 nodes in the DAG, then the FSW would be used and you would have 5 votes overall. If your primary site goes down, then you only have 2/5 votes online, no quorum majority, and the DR site will require manual activation using the steps I provided in the article.

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
 
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osiexchange

Thanks for all this info. Just a couple more questions. If the FSW is not used, does it hurt to have it there? I believe it was required when I created the DAG. Second, the DAG has an attribute called alternate file share witness. So, with four nodes total, two in each site, my main FSW in the primary datacenter and the alternate FSW which is on a server in the DR site, if the primary goes down, would the alternate file share witness count as a vote?

I am concerned about your first comment above about 1/3 votes.... Our DR site is somewhat unstable and experienced power fails. The third node may not always be available so if I lose a node in my primary site and the DR site is offline, I'm in trouble. Would having a total of 4 nodes in the DAG prevent this?

Again, thanks for all this info.
 
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Brian Day MCITP

The FSW is required to be part of a DAG configuration at all times because it is used as you add/remove nodes.

1st node added to DAG, FSW not in use.

2nd node added to DAG, FSW is in use.

3rd node added to DAG, FSW not in use.

Etc... :)

The Alternate FSW is never used unless you perform a manual Datacenter Switchover; and when it is used it replaces the normal FSW. It should be covered in the link above somewhere. So the short version is, no, the AFSW does not count as a vote.

If the DR site isn't stable, then you want enough votes in the primary site so that it won't affect the majority. You could do this be adding a 4th node to the DAG in the primary site, and then he FSW would also be in use. Then you'd have 3 nodes in the primary and 1 in the DR site, so if the DR site goes down you'd still have 4/5 votes (3 nodes + FSW) online and quorum majority would be maintained.

Now that 3rd node in the primary site means you'll need another Windows Server Enterprise with the mailbox role installed. If you have dedicated hub/cas servers in the primary site then you could just load one up with Enterprise and add the mailbox role with no databases housed on that server.

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
 
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osiexchange

Well, my CAS/Hubs are already buiilt and in production and they are running Standard Edition of Windows and Exchange. I can however stand up a Public Folder server on Windows Enterprise in my primary site and install the mailbox role on it. I was planning on having the Public Folders on the two mailbox servers I have now but I think its better on a separate server because I can't do full server switchovers with a public folder database on the servers and the PF server would be the extra vote I needed.

So with this configuration, I have only one node in my DR site so if my primary goes down, I need to use the link above to bring up the databases in my DR site? If so, I guess I can live with that.
 
J

James-Luo

With your current design, yes, you need to follow the article above to bring up the database in DR


 
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