DAG over WAN ?

KratosDefense
KratosDefense used Ask the Experts™
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Im deploying exchange 2010. Im planinng on using DAG for database HA. Can you use DAG over a WAN? what is recommended in this senario?
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Solutions Architect
Commented:
yes DAG can surely be used over a way, what is the bandwidth of your wan ?

Author

Commented:
3mb
AkhaterSolutions Architect

Commented:
you should have no issues, just keep in mind that DAG does NOT take into consideration link failures so you'd better turn off automatic failover off for the server in the remote site
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you want to have less than 250ms latency
AkhaterSolutions Architect

Commented:
the 250ms latency is MS recommendation but it doesn't mean anything by itself IMHO. you can ping almost any website with < 250ms latency.
BusbarSolutions Architect
Commented:
Adding, the 250 to become within the supportability boundary more than this will work but not supported
you could always configure the dag copy in the remote site with replay lag time
this would cause active manager to select another server with a copy first, unless there is a serious issue with the other local copy

Author

Commented:
Ok good stuff here. How about the impact the log shipping and database copies will have on my wan link. Im concerned that the data sync between exch 2010 MB servers might cause wan congestion. thoughts?
If you have at least two nodes in primary and one in the secondary site your can utilize datacenter activiation coordination mode
Set-DatabaseAvailabilityGroup -Identity DAG1 -DatacenterActivationMode DagOnly

this traffic will depend on the size of the database and amount of message sent/received daily

Here is an article on planning for ha
http://technet.microsoft.com/en-us/library/dd638104.aspx

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