Exchange s Search for High Availability in Visual C#

Generation Quick Response Code in Visual C# Exchange s Search for High Availability

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If you don t assign an IP address or set the value to 0.0.0.0, Exchange will attempt to lease an address using DHCP. If you use DHCP, Exchange will report the IP address as 0.0.0.0 any time that you look at the DAG properties with the Get-DatabaseAvailabilityGroup cmdlet.

access to the FSW from the other datacenter creates a condition where the FSW is inaccessible and cannot be used to maintain quorum. It is therefore better to create two DAGs and locate an FSW in each datacenter.

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Microsoft s preferred approach is that you use its continuous replication technology to maintain database copies within a DAG. They also support a replication API to allow other vendors to build DAG solutions with their own feature set. Assuming the third-party solution is installed and available, these DAGs are created with the NewDatabaseAvailabilityGroup cmdlet using the ThirdPartyReplication parameter. Once a DAG is created based on a third-party solution, it cannot be changed. If you want to revert to use the Exchange technology, you have to remove all servers from the DAG, remove the DAG, and then re-create it.

See the Microsoft Web site for a current list of approved third-party replication solutions for Exchange 2010 .

Immediately after creation, a new DAG is an empty container that is waiting to be filled with mailbox servers and their databases that bring functionality to the DAG. Being able to construct a DAG gradually over time is one of the advantages that the implementation brings to Exchange. The alternative, which we see in the implementation of clustered mailbox servers in Exchange 2007, is to install all of the servers in the cluster at one time. After

the DAG is created and its properties verified, you can start to add mailbox servers to the DAG before creating new database copies that will be managed by the servers. This process doesn t have to begin immediately and you can keep an empty DAG in the organization for as long as you need to before you begin to add servers. Servers are added and removed from the DAG using the Manage Database Availability Group Wizard through EMC or by using the Add-DatabaseAvailabilityGroupServer and Remove-DatabaseAvailabilityGroupServer cmdlets. To begin to manage DAG membership with EMC, go to the Mailbox section of the Organizational Configuration node and select the DAG from the Database Availability Groups tab, then right-click to reveal the menu options for DAG management (Figure 8-10).

Microsoft recommends that you don t install Exchange on a domain controller . It therefore follows that they re not particularly excited if you add a mailbox server that happens to run on a domain controller to a DAG . Exchange doesn t block this action and you can go ahead and use a domain controller if you really must; hopefully, you will only do this in a test configuration and not in production use .

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After a mailbox server is added to a DAG, you can manage its membership in the DAG from another Exchange server. Some administrators prefer to use Server Manager to install the Windows Failover Clustering feature (Figure 8-11) before they attempt to add a server to a DAG because they prefer to make sure that all of the prerequisites are in place before they proceed.

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The following steps occur to instantiate a DAG with the addition of the first mailbox server. Exchange has to do quite a lot of work to bring a server into a DAG, especially if it has to install Windows Clustering, so this process does not happen quickly.

2. If not present, Exchange installs Windows Failover Clustering on the mailbox server. 3. A failover cluster is created using the name of the DAG. 4. A cluster network object (CNO) is created in the Computers organizational unit (OU)