Installing vCenter Server in a Linked Mode Group
If your environment exceeds the recommend limits of a single vCenter Server instance, then vCenter Server 4.0 allows you to install multiple instances of vCenter Server and
have those instances share inventory and configuration information for a centralized view of all the virtualized resources across the enterprise.
Table 2.1 shows the maximums for a single instance of vCenter Server. Using a Linked Mode group is necessary if you need to manage more than the number of ESX/ESXi hosts or virtual machines listed in Table 2.1.
Maximum Number of Hosts or VMs per vCenter Server
ESX/ESXi hosts per vCenter Server Virtual machines per vCenter Server
vCenter Server Linked Mode uses Microsoft ADAM to replicate information between the instances. The replicated information includes the following:
• Connection information (IF addresses and ports)
• Certificates and thumbprints
• Licensing information
• User roles
In a Linked Mode environment, there are multiple vCenter Server instances, and each of the instances has its own set of hosts, clusters, and virtual machines. However, when a user logs into a vCenter Server instance using the vSphere Client, that user sees all the vCenter Server instances where they have permissions assigned. This allows a user to perform actions on any ESX/ESXi host managed by any vCenter Server within the Linked Mode group.
Before you install additional vCenter Server instances, you must verify the following prerequisites:
• All computers that will run vCenter Server in a Linked Mode group must be members of a domain. The servers can exist in different domains only if a two-way trust relationship exists between the domains.
• DNS must be operational. Also, the DNS name of the servers must match the server name.
• The servers that will run vCenter Server cannot be domain controllers or terminal servers.
Each vCenter Server instance must have its own back-end database, and each database must be configured as outlined earlier with the correct permissions. The databases can all
reside on the same database server, or each database can reside on its own database server.
After you have met the prerequisites, installing vCenter Server in a Linked Mode group is straightforward. You follow the steps outlined earlier in "Installing vCenter Server" until you get to step 9. In the previous instructions, you installed vCenter Server as a standalone instance in step 9. This sets up a master ADAM instance used by vCenter Server to store its configuration information.
This time, however, at step 9 you simply select the option Join A VMware vCenter Server Group Using Linked Mode To Share Information. When you select to install into a Linked Mode group, the next screen also prompts for the name and port number of a remote vCenter Server instance. The new vCenter Server instance uses this information to replicate data from the existing server's ADAM repository.
After you've provided the information to connect to a remote vCenter Server instance, the rest of the installation follows the same steps described previously. After the additional vCenter Server is up and running, logging in via the vSphere Client displays all the linked vCenter Server instances in the inventory view
Installing vCenter Server is just the beginning. Before you're ready to start using vCenter Server in earnest, you must first become a bit more familiar with the user interface and how to create and manage objects in vCenter Server.