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Need Exchange HA Recommendations - 9.Dec.2013 1:20:38 PM

cricebrite

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Joined: 9.Dec.2013
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I have a customer that has two locations with a point to point connection that is looking for a new exchange environment with some high availability. My thought process would be to have 2 servers at each location. One with the cas/ht roles and the other with the mailbox role. I believe I have the DAG portion all figured out, since if I'm correct you can use DAG accross multiple subnets but I'm trying to process the best way to setup HA for the CAS/HT roles. Any suggestions would be greatly appreciated.

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RE: Need Exchange HA Recommendations - 9.Dec.2013 2:36:31 PM

de.blackman

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From: Toronto, Canada
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CAS\HT roles provide high availability by using Client Access Array (CAS Array). This is a collection of CAS servers within the same AD site/subnet. HA is provided for these machines using hardware/software load balancers.

In short, to implement HA for CAS role, install 2 servers in the same site/subnet and load balance them. This is the same for inbound SMTP on the hub transport role. For outbound SMTP, simply put both the servers as source servers on the Send Connector.

My usual design for such a scenario is:

Primary Site will contain:
2 Servers running the three roles (Mailbox, hub transport and Client access roles)
1 Load balancer

Secondary site will contain:
1 Server running the mailbox, hub transport and client access roles

This design provides you HA at the primary site PLUS DR to a secondary site.

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Ibrahim Benna - Microsoft Exchange MVP
Forum Moderator
Navantis
@IbrahimBenna

(in reply to cricebrite)

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RE: Need Exchange HA Recommendations - 9.Dec.2013 2:41:52 PM

cricebrite

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Joined: 9.Dec.2013
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I'm not sure if this helps at all and I forgot to mention, that my plan would make this an active/active environment as there are users at both of these locations, but would make one of the locations primary for CAS and HT roles. If this site went down, what would be the best method to failover the CAS/HT roles to the other location?

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RE: Need Exchange HA Recommendations - 10.Dec.2013 7:54:51 AM

de.blackman

Posts: 3542
Joined: 4.Apr.2005
From: Toronto, Canada
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You cannot make it active\active without having CAS\HT in both sites. You must place a CAS server in the same site a mailbox server is placed. All users in site 1 will connect to the CAS server in site 1 to connect to their mailboxes hosted on MBXServer1. The same is true for users in site 2.

For the hub transport server, create a single send connector to the internet and add both servers from both sites and they can send emails to the internet independently. OR create two different send connectors, one for each site and they can send emails individually through their local sites.

Because you have two different AD sites, Site1 being the primary and the internet-facing site, the CAS server will have all the external URLs on it. CASserver2 in site2 will not have any external URLs registered. You will need change the DNS record for the CAS Array in Site1 to point to the IP address of CAS Array2 in site2. Because Outlook clients connect to the address registered as the RPCClientServer, which generally is the same as your CAS Array name, changing the IP to point to the other site will allow clients to reconnect as long as their mailbox databases have been activated on MBXServer2.

_____________________________

Ibrahim Benna - Microsoft Exchange MVP
Forum Moderator
Navantis
@IbrahimBenna

(in reply to cricebrite)

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