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Exchange 2010 license requirement on passive node

I'm on planning setting up High Availability for our exchange 2010 ent edition, we will use Double-Take as HA solution and setting up ( active-passive ) HA.
My concern now, do we need to purchase another license for exchange server on passive node although it just running as passive ?
4 Solutions
BusbarSolutions ArchitectCommented:
Yes, you will need to buy Exchange server license for that
Bruno PACIIT ConsultantCommented:

It depends of what you mean saying" Active-Passive" with Double-Take.
Does the "passive" server is up and running ? Or is it a sort of VM copy that is not started ?

In the first case: yes, as Exchange 2010 services are installed on the "passive" server and as this server is up and running, you need a Exchange 2010 server license for it.
In the seconde case: no, you don't need a license for a server that is not running.

Are you really sure that HA with double-take is the best way to provide HA on Exchange 2010 !?? I strongly doubt about that.

Have a good day.
motioneyeAuthor Commented:
Do you have any recommendation besides Double-Take ? I heard about  DAG, but our exchange 2010 ent running on win 2008 std edition, which I think not meet requirement for DAG fail over.

Yes our passive is ON and since double-Take will set the replication between two exchange to replicate real time data. ut it is not accessible since it must be fail over in order to bring teh exchange online ( hence accepting client request )
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Bruno PACIIT ConsultantCommented:

Yes a DAG requires Windows 2008 Enterprise because of Windows Failover Clustering.
Is this a real problem for you ?? You can upgrade easily to Enterprise version as it is ONLY a matter of Activation Key.
Exchange 2010 Standard Edition is enough for a DAG. If you don't need functionalities of the Enterprise version of Exchange then stay on Standard Edition.
To resume : Windows 2008 Enterprise is requires, Exchange 2010 Standard is enough.

Of course DAG is the best way to have HA.
With only 2 Exchange servers you can reach a HA level that may suffice for a lot of enterprises. At least as much as Double-Take.

With only 2 servers to create the DAG and no other servers for CAS role or expensive hardware load balancer, in case of failover an admin will have to make a change on a DNS record so that clients are able to reach the failedover server.
Anyway, it's the same with Double-Take. The difference is that with Double-Tak you click on a button to launch the failover process and the DNS changes are supposed to be made by this process. With Exchange, an admin has to make the change in the DNS console.

The big difference is that DAG protects data against file corruption. The DAG replicates transactions between servers, it does not replicate files as Double-Take does.
So if something (let's say a virus) corrupts the database file on the first Exchange server od a DAG, the corruption is not replicated to the other server.
Double-take replicates file modifications... So Double-Take replicates the corrupted files.

DAG is an Exchange native process, Double-take is not.

Also, you have to think about "failback"... If the crash was only due to some hardware problem and datas have not been lost (this is the most frequent case), with a DAG you don't have to "reseed" the database. Exchange DAG will restart transaction synchronization in the opposite way (from the failedover server to the origin server).
With Double-Take, even if the failback process can be initiated by a single push button, the process creates a full replication job from the failedover server to the origin server. That will take much more time to finish.

I never used Double-Take for Exchange but I many times installed Double-Take for some customers to protect many servers (file servers usually, VMs often, database servers sometimes, and even DC !!! yes... why the hell someone want to duplicate DCs with double-take... ask my customer).

I must say that I'm not really confident in Double-Take reliability and efficience.

If the failover process is quiet simple, the failback is almost always a nightmare.

If you're "fluent" with Double-Take it may be the easiest for you as Exchange DAG needs some understanding of Exchange. If you want to consider Exchange as a black-box then Double-Take is may be the easiest for you.
What I just wanted to say is that in my string opinion IT IS FAR TO BE TO BEST WAY.

Have a good day.
Simon Butler (Sembee)ConsultantCommented:
Need to correct something posted above.
The upgrade of Standard Windows to Enterprise Windows is not just a matter of putting a key in to the application and is not a supported modification. It requires the reinstallation of Windows.

Furthermore, if you wait a little longer you can do high availability of Exchange 2010 using Windows 2012 STANDARD edition. You just need to wait for Exchange 2010 SP3 to be released.

This has to be the first time I have heard of anyone actually considering the implementation of DoubleTake for Exchange 2010. If you don't already own the product I would strongly suggest looking at putting the funding towards using the native solution for high availability instead. It is much easier to get support and assistance.

Bruno PACIIT ConsultantCommented:
Hi again,

Sorry, I was not precise enough... you can easily upgrade from standard to enterprise on Windows 2008 R2 : http://blogs.technet.com/b/server_core/archive/2009/10/14/upgrading-windows-server-2008-r2-without-media.aspx

And it is supported as I already done that on Microsoft advice...
Again, it's about R2... My apologies for miss of precision.

Have a good day.
Simon Butler (Sembee)ConsultantCommented:
You are still wrong. While the change is supported by Microsoft - it isn't supported when Exchange is involved:

"If you're installing the Mailbox server role and you intend the server to be a member of a database availability group (DAG), you must be running the Enterprise Edition of Windows Server 2008 or Windows Server 2008 R2. The Standard Edition doesn't support the features needed for DAGs. You can't upgrade Windows when Exchange is installed on the server. "

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