Active \ Active Site Resiliency Model

[SYSTEM]

We have a customer who has two sites:

Site A: 700 users and Site B: 150 users

We had initially recommended Active\Passive Site Resiliency model where we had two mailboxes with one fsw in the primary site and the DR site with one MBX hosting all passive copies.

Customer needs the DR site to be highly available and also requires that the 150 users in site B access their mailboxes on mbx servers in site B itself. In short customer is looking at Active \ Active scenario now.

From what I understand the best way to go about with it to host two Dags with 3 MBX servers each (4 incase of HA). I guess the configuration should look like below:

1) Dag 1 : Two Mbx’s in Site A hosting Active Passive copies , One FSW in Site A and One Mbx in Site B hosting passive copies
2) Dag 2: Two Mbx’s in Site B hosting Active Passive Copies, One FSW in Site B and One Mbx in Site A hosting passive copies.

Please advice if this is the right approach or if there are any other alternatives and best practices.

The only concern is that the number of mailboxes for the configuration is high considering that there are only 850-900 users.

[SYSTEM]

in Active/Active scenarios the recommendation is two DAGs as you described. Mainly to avoid failovers because of WAN outage – so active DB at siteB will stay at siteB with two DAGs.

Keep in mind that additional costs for that approach (especially looking at the small number of your mailboxes) is huge – amount of servers, name spaces and so …

FSW comes into play only by odd number of servers.