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?