Situation:In Exchange 2007, the Outlook client gets disconnected whenever we have a cluster failover/hand-off. The disconnection time depends on the design. Let’s say it’s a stretched CCR cluster on Windows 2008 and they don’t span the subnet. If they don’t adjust the DNS host record TTL, it could be 15 minutes before the Outlook clients expire the local cache entry and pick up the CMS’ new IP address.Talking Points:If a CAS server in a CAS array fails, then Exchange clients simply connect through another CAS Server.For Mailbox failures: Since a failover now only involves a database, rather than an entire server, the failover time has been reduced to around 30 seconds which considerably improves the client experience.Slide Objective:In Exchange 2010 with all clients connecting through the CAS Server, the client experience is improved for any failures.
Talking Points:Here is Tomas Navarro’s new Exchange 2010 environment. Tomas is the lead Exchange and Active Directory administrator for Contoso. He has overall responsibility for providing messaging and communications services to all of Contoso’s employees. Tomas’ primary challenge is to maintain high levels of availability with a flat or shrinking budget year-over-year. There are 5 servers in the main datacenter in San Jose that host mailboxes. These mailbox servers are grouped to provide automatic failover. The group of servers is known as a Database Availability Group. Each mailbox database has 3 instances, which we’ll refer to as copies, <click> placed on separate servers to provide redundancy. At any given time, only 1 of the 3 database copies is active <click> and accessible to clients. <Click> This gives us database centric failover and <click> all the failover is managed within Exchange.The Client Access Server <click> manages all communications between clients and databases. Outlook clients no longer connect directly to mailbox servers, as they did in previous versions of Exchange.When a client such as Outlook connects to Exchange, it first contacts the CAS Server. The CAS Server determines <click> where the user’s active database is located ( in our case the user is on DB1 which is currently active on Mailbox Server 1), and forwards the request <click> to the appropriate server. When the client sends an e-mail <click>, the active database is updated. Then, through log shipping <click>, the other 2 passive copies of the database are updated. <click>Let’s say that a disk fails <click>, affecting one of the databases on Mailbox Server 1. In previous versions of Exchange, the administrator would need to failover all the databases on Mailbox Server 1 to recover from this failure, or else restore the Database 1 from a tape backup. However, Exchange’s new architecture supports database-level failover, so Database 1 has automatically fails over to Mailbox Server 2 <click> without affecting the other databases. The Outlook client, having lost its connection to the database, automatically contacts the CAS Server to reconnect. The CAS Server determines which mailbox server has the active copy of the users’ database. It connects <click> the client to Mailbox Server 2. When new mail is sent <click>, the active database on Mailbox Server 2 is updated. The second copy of the database <click> is also updated through log shipping. The end user is unaware that anything has happened, and Tomas can replace the failed disk drive at his leisure. The administrator can set up to 16 copies per database to meet the Service Level Agreements for his users. For a special category of users, Tomas keeps a 4th database copy on a mail server in a geographically remote location <click>. This server is located in a different Active Directory site, but is kept up-to-date over the Wide Area Network using the same replication technology as the other servers. (No stretching of subnets) If a hurricane, earthquake, or other catastrophe should shut down the main datacenter, this remote server can be activated and readied for client access in about 15 minutes.Slide Objective:Describe how the new High Availability solution works, including stretching the solution across sites.