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Two Exchange Server Site Resiliency

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Two Exchange Server Site Resiliency - 20.May2011 7:35:39 AM

InfMail

Posts: 5
Joined: 20.May2011
Status: offline

We have two locations either side of the Atlantic, configured as two AD sites. Currently all email services are hosted at site1, access over a VPN for users in site2.

We intend to install an Exch2010 server, using a typical install, at site2 . Mailboxes of those located in site2 will be move to the mail server at site2.

We�d like to add some support for disaster recovery (DR) by having a copy of each sites mailbox DB on the other site. This is primarily for Site Resiliency, rather than High Availability. The intention is to activate the passive copy in the event of a failure at either site.
It�s proposed that both CAS roles are configured with the same external URLs for OWA, ActiveSync , etc; with DNS set to the server in site1.

In the event of DR we�d modify DNS, MX to the server in the remaining site.

Does adding a Witness Files Share (WFS)in a Hub Transport mean we�d have to buy another Exchange 2010 license ?

Is a WFS required for this scenario: Resiliency only?

Can the WFS be on a non Exchange server and what are the real implications of doing so ?
Any further advice ?

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RE: Two Exchange Server Site Resiliency - 22.Jun.2011 3:21:36 PM

travis.sheldon

Posts: 359
Joined: 16.Sep.2010
Status: offline

It�s proposed that both CAS roles are configured with the same external URLs for OWA, ActiveSync , etc; with DNS set to the server in site1.

This is a bad idea unless you're using subdomains to assign/use for each site or you do split DNS..you'll want to have the CAS urls pointing to the respective CAS server in each site..by doing it your way, clients will connect to the CAS server in site1 (regardless if theyre in site2) and then proxy to the mailbox server.

eg if you do outlook.domain.com for both CAS servers, then both sites will connect to one CAS server unless you're using split DNS.

You can do outlook.site1.domain.com and outlook.site2.domain.com, and in the event of a failure at site2 (or 1), change the IP to fail over site.

Or, if you do split DNS then you'd have outlook.domain.com, and the local DNS server at each site will CNAME outlook.domain.com to their respective CAS server in site. In the event of a failure, you'd modify the local DNS CNAME record to point to the fail over site. This method requires less work during a fail over, but has it's limitations (ie, if active directory or the DNS role fail or that each site has to manage DNS)

If you're doing a 2 server solution in the DAG then you will have to use a WFS..the job of the WFS is to act as a tie breaker between the servers in the DAG. You do not need to pay for another Exchange license for WFS as it's just a 'file share' (ie, you can use a linux server and samba or just a windows share). By default, Exchange will try to use the HUB server as the WFS if the HUB server is not installed on mailbox server.

Post #: 2