Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 1162
  • Last Modified:

Exchange 2010 DAG/ Quorum queries

Hi

I'm trying to understand Exchange 2010 HA, but can't seem to get my head around DAG/FSW/DAC concepts.

Let me give an example situation:

Two datacentres (DataC's). Each DataC has roughly the same number of users. We have one DAG, that is spread across both DataC's. The DAG contains 4 mailbox servers in SiteA and four mailbox servers in SiteB. The FSW is a Hub/CAS in SiteA. Active databases are spread across both sites.

Now, I have keep reading about Exchange "maintaining quorom" - could someone please explain what that means to me? I really don't understand where quorom fits into this as we are not using standard Windows clustering. Is the quorom an actual file, like it was in Exchange 2003?

My understanding is this, and I would be really grateful if someone could point out where I am wrong:

a) Each mailbox server has one vote
b) The server that is locked to the FSW has one vote (and this will always be SiteA)
c) For SiteA, there will always be 5 votes, for SiteB, there will always be 4.

Now, let's say a WAN critical event happened, and SiteA lost connection to SiteB.  Am I correct in thinking that all the DB's will mount in SiteA because it "has quorom", i.e. it has the majority votes?

And, in this situation, is there any benefit to having the FSW located in a completely different, i.e. third, DataC?

http://technet.microsoft.com/en-us/library/dd979799.aspx
0
richlionel
Asked:
richlionel
2 Solutions
 
Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
Quorum also known as FSW (File share witness) it just acts as a dummy Partner to DAG in case of Majority required.

In E2k10 you need to have the majority to remain Active host of the Database and resources :)

Exchange 2010 doesnt use the full Cluster so its just a part of it .... Nopes Quorum isn't whats in Exchange 2003.

As we know, Exchange Server 2007 supported three different kind of high availability methods which varied from the single server to across multiple Exchange servers. And then, Exchange Server 20010 introduced Database Availability Group (DAG) which is essentially a collection of at least two and maximum 16 mailbox servers to achieve the high availability.

You should be familiar with the term, File Share Witness (FSW) if you have already implemented the CCR in the Exchange 2007 environment. As the name suggest, file share witness is a file share residing on the third server outside of the DAG for ensuring quorum availability in the cluster. We can provide the file share witness directory and share name while creating the DAG.  Unlike Exchange 2007, where Microsoft recommended hosting file share witness on the Hut Transport server, Exchange 2010 provides you full control to host file share witness on non-Exchange Server as well, but you have to add the Exchange Trusted Subsystem Universal Security Group to the local Administrator Group on the FSW Server


Answers:
a). absolutely correct :)
b). Perfect !
c). My vote also :) (correct)


Now, let's say a WAN critical event happened, and SiteA lost connection to SiteB.  Am I correct in thinking that all the DB's will mount in SiteA because it "has quorom", i.e. it has the majority votes?
Yes they should be .....

And, in this situation, is there any benefit to having the FSW located in a completely different, i.e. third, DataC?
In this case what would happen all sites loose connectivity to each other ??

- Rancy
0
 
Exchange_GeekCommented:
Your doubts are answered by DAG-Guru at Microsoft on the below mentioned link.

http://blogs.technet.com/b/exchange/archive/2011/05/31/exchange-2010-high-availability-misconceptions-addressed.aspx

Apparently after the TechEd, it seemed everyone had the same doubts that you've got, it is not something exceptional - these are normal questions. So, a really good write up has been written on it. I wouldn't like to copy paste and spoil it up. So, please read once and ask questions if any.

Happy Weekend.

Regards,
Exchange_Geek
0

Featured Post

Has Powershell sent you back into the Stone Age?

If managing Active Directory using Windows Powershell® is making you feel like you stepped back in time, you are not alone.  For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now