FileWitnessShare on ThirdSite or UsersSite. Why not ?

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Shahid Roofi



Assuming the scenario of equal number of DAG nodes at two datacenters(primary and DR) and users residing at third site.

Why is it that, MS is recommending FWS to be on a primary site instead of third site which can be a site where users reside for e.g.

In that later case, geo cluster can work in full swing with MNS cluster. If the users site, looses connectivity to primary datacenter but NOT the DR, the databases would be dismounted due to loss of quorum (due to MNS rules) at the primary site, and services would be up from the DR automatically. Is there any problem in reliability of exchange databases in that case ? or some particular problem with exchagne 2010 DAG architecture doing that ?

If we keep FWS on the primary site, automatic failover and resume of services at DR is not possible because of MNS, majority nodes rule.

Then ofcourse there would be manual work to brings things up at DR. It would not really be a geo cluster in that case. (i remember it would resemble to SCR in Exchange 2007 with less number of steps though)

Also DAC mode is also not required in this case i believe because of placement of FWS at third site.
 
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esylo

I agree that his should be the way to acheive automatic failover as long as you have reliable connectivity between all sites. That is what we are looking into as well.
 
J

Jonas Andersson [MCITP]



A little tip...

Do a little checklist with different "real-life" scenarios and how you should and could handle them

Jonas Andersson MCTS: Microsoft Exchange Server 2007/2010 | MCITP: EMA 2007/2010 | MCSE/MCSA Blog: http://www.testlabs.se/blog
 
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James-Luo



“Although it's supported to use a witness server in a third datacenter, we don't recommend this scenario. From an Exchange perspective, this configuration doesn't provide you with greater availability. It's important that you examine the critical path factors if you use a witness server in a third datacenter. For example, if the WAN connection between the primary datacenter and the second and third datacenter fails, the solution in the primary datacenter will become unavailable”

----------Refer to <Managing Database Availability Groups>

James Luo

 
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esylo

Yes, but this is assuming that the network links between the datacenters are unreliable...
 
A

AndyD_ [MVP]



and note they use the words "primary", "secondary" etc...

If you have 2 datacenters that are peers, then a 3rd datacenter that holds the FSW makes sense.
 
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Shahid Roofi



Very correct. That's because if you loose connection to the FSW site( which is the users site also), it does not really matter, weather the database would go mounted from datacenter1 or not. instead to add to the beauty of solution, any datacenter would bring it's databases up which connects to FSW site giving users the access and at the same time other datacenter would get dismounted, preventing divergence !
 
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