Hi Thank you for all your replies. This has given me a better understanding of what is expected to happen.
One more question though. (For the moment) When an exchange server fails and all the clients reconnect to another exchange server. What happens when the original exchange server becomes available again? Do the Outlook clients automatically change back to using their original Exchange server? Or do they just continue to connect to the server that they have been connected to whilst their (home) server was off line? I am just thinking about our circumstances where we have one exchange server in the UK and one In the US. It would seem illogical for the clients to continue to connect to a server in the US if the one in our office became available again after a failure. And vice versa should a failure occur on the US server. Regards Kevan Dickinson Network Manager NSF-CMI 23 Lodge Road Hanborough Business Park, Long Hanborough, Oxford, OX29 8SJ, UK T:+44 01993 885661 E:kevan.dickin...@nsf-cmi.com W:www.nsf-cmi.com From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: 07 April 2011 01:11 To: MS-Exchange Admin Issues Subject: RE: Questions about DAG's (Database Availability Groups) in exchange 2010 In order to answer this question completely (and accurately) depends on a full understanding of your topology and Exchange deployment. The best I can say to some of your questions, based on what you've told us, is: it depends. :) Failover within a DAG happens automatically. Given healthy replication and 80ms or less latency between the servers, you should see failover within 30 seconds. FailBACK (which is actually referred to as a "switchover") is a manual process. Insofar as how communications happens with HTs and CAS - insufficient data. Having a GLBS makes some things easier, but if you have redundancy designed into your topology, it isn't necessary - but it depends on what you are protecting and how you've done your implementation. There is a great deal of flexibility that allows you to design to meet the specific needs of your company and the behavior is dependent on that design. Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Kevan Dickinson [mailto:kevan.dickin...@nsf-cmi.com] Sent: Wednesday, April 06, 2011 6:09 PM To: MS-Exchange Admin Issues Subject: Questions about DAG's (Database Availability Groups) in exchange 2010 All. This is our Current setup. Exchange 2010 servers in the UK and the US both in the same Exchange organization. At the moment we are running a Windows 2003 Domain structure. The UK domain is a child domain of the US Domain. I was wondering if someone could answer a question for me about DAG's in Exchange 2010. It is something I would like to understand in case we would like to implement it. My understanding of a DAG is that it is a replication of the Mailbox database attached to an Exchange 2010 server to another site / server in case the main database becomes corrupt. However what happens If the actual server that the mailbox database is attached to becomes unavailable will the users who have mailboxes on the unavailable server be automatically diverted to another server where the replicated database is? Or would you need to attach the replicated database to another server manually in order for users to become attached to their email again? What would happen in a situation like ours if say we replicated our Database to our office in the US and our server became unavailable. Would the office in the US need to manually mount our database on their server and then all our external and internal users need to change their outlook settings to look for client.USCompany.org? Instead of client.ukcompany.com If so presumably there mail would then get routed via there anti virus / spam filtering software? I am trying to work out what is the best way to get better exchange redundancy in the event of either the An US Exchange 2010 server or ours being becoming unavailable? Presumably everything would be much easier if we had one Exchange Gateway, or does this not matter really? At the moment email in the UK enters via our Mail gateway / anti virus and anti spam system and email in the US enters via there gateway. You help and comments would be appreciated. Regards Kevan ******************************************************************************** ***Disclaimer*** The contents of this Email may be privileged and are confidential. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. 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