Hi all,

We are planning a migration from 2010 to 2013 with a large DAG across 2 Datacenter. 4 mbx servers per Datacenter. Splt

Split DNS + unbound model will be used => for a given DC 50% of the trafic is proxied from the other DC

After reading the placemeent in a 3rd DC for FSW one question spring to mind : 

• in event of DC failure everything goes online to other DC by auto failover
• in the event of WAN faillure betwen 2 DC. Obviously, each dbs will stay up in each DC. BUT proxy wont work...

So let's say user1 has his mbx hosted on DC2. Load Balancing (F5) send request to a cas named CAS1 in DC1. CAS1 proxy the request to a MBX in DC2. user1 is happy :)

but in cas of wan failure ? CAS1 cannot proceed a cross site proxy request ... what happenned ? 

in this case, should we put all db active on only dc and update F5 VIP and dns record to make sure CAS1 will do only local proxy request ?

i hope i made myself clear

regards

 

Actually I believe that the servers in the site that does not hold the Primary Active Manager (PAM) won't be able to see the PAM (the cluster group owning node), and therefore will dismount their

so,

lets assume dc1 : 4 members + pam / dc2 : 4 members. FWS still in DC3

a wan failure occurs betwen dc1 and dc2.

members in dc1 can lock the FSW. members in dc2 can as well lock the fsw.

but because PAM is located in DC1 and can get the quorum (5) all the dbs will be mount on DC1 and all dbs will be dismount in DC2 auto ?

so it s exactly the same scenario during a DC failure with FSW in third site

I hope its make sence !

thx

so,

lets assume dc1 : 4 members + pam / dc2 : 4 members. FWS still in DC3

a wan failure occurs betwen dc1 and dc2.

members in dc1 can lock the FSW. members in dc2 can as well lock the fsw.

but because PAM is located in DC1 and can get the quorum (5) all the dbs will be mount on DC1 and all dbs will be dismount in DC2 auto ?

so it s exactly the same scenario during a DC failure with FSW in third site

I hope its make sence !

thx

• Marked as answer by Amy.WangMicrosoft contingent staff, Moderator 22 hours 15 minutes ago

so,

lets assume dc1 : 4 members + pam / dc2 : 4 members. FWS still in DC3

a wan failure occurs betwen dc1 and dc2.

members in dc1 can lock the FSW. members in dc2 can as well lock the fsw.

but because PAM is located in DC1 and can get the quorum (5) all the dbs will be mount on DC1 and all dbs will be dismount in DC2 auto ?

so it s exactly the same scenario during a DC failure with FSW in third site

I hope its make sence !

thx

• Marked as answer by Amy.WangMicrosoft contingent staff, Moderator Friday, April 17, 2015 9:11 AM

That's the way I understand it.

thx ED :)

You're welcome, happy to help.

The behavior you describe is correct, but not for that reason. It only seems like the PAM is locked, but it really is the FSW that arbitrates. The current PAM gets a 6-second headstart to lock the PAM, but if it cannot, the other site will remain active.

You can see the difference if you imagine a power outage in the datacenter that currently hosts the PAM. It will take an extra six seconds, but the other site will lock the FSW and mount all of the databases.

• Proposed as answer by Ed CrowleyMVP 37 minutes ago

Thanks for the clarification.  I figured the FSW had to have a part in it.