Using vCenter Server in Linked Mode
You can join multiple vCenter Server systems using vCenter Linked Mode to allow them to share information.When a server is connected to other vCenter Server systems using Linked Mode, you can connect to that vCenter Server system and view and manage the inventories of the linked vCenter Server systems.
Linked Mode uses Microsoft Active Directory Application Mode (ADAM) to store and synchronize data across multiple vCenter Server systems.Each ADAM instance stores data from the vCenter Server systems in the group, including information about roles and licenses. This information is replicated across all of the ADAM instances in the connected group to keep them in sync.
When vCenter Server systems are connected in Linked Mode, you can perform the following actions:
Log in simultaneously to vCenter Server systems for which you have valid credentials.
Search the inventories of the vCenter Server systems in the group.
View the inventories of the vCenter Server systems in the group in a single inventory view.
Linked Mode Prerequisites for vCenter Server
The following requirements apply to each vCenter Server system that is a member of a Linked Mode group:
vCenter 4.x and vCenter 5.x linking not supported: Linked Mode groups that contain both vCenter Server 5.0 and earlier versions of vCenter Server are not supported. The vSphere Client does not function correctly with vCenter Servers in groups that have both version 5.0 and earlier versions of vCenter Server. Do not join a version 5.0 vCenter Server to earlier versions of vCenter Server, or an earlier version of vCenter Server to a version 5.0 vCenter Server. Upgrade any vCenter Server instance to version 5.0 before joining it to a version 5.0 vCenter Server.
Only vCenter Standard Edition supported: To join a Linked Mode group the vCenter Server must be in evaluation mode or licensed as a Standard edition. vCenter Server Foundation and vCenter Server Essentials editions do not support Linked Mode.
DNS is primary requirement: DNS must be operational for Linked Mode replication to work.
Trust relationship is must for cross domain linking: The vCenter Server instances in a Linked Mode group can be in different domains if the domains have atwo-way trust relationship. Each domain must trust the other domains on which vCenter Server instances are installed.
Admin privileges on both the vCenter for linking vCenter: When adding a vCenter Server instance to a Linked Mode group, the installer must be run by a domain user who is an administrator on both the machine where vCenter Server is installed and the target machine of the Linked Mode group. Each vCenter Server user sees the vCenter Server instances on which they have valid permissions.The vCenter Server instances in a Linked Mode group do not need to have the same domain user login.The instances can run under different domain accounts. By default, they run as the LocalSystem account of the machine on which they are running, which means that they are different accounts.
Time synchronization All vCenter Server instances must have network time synchronization. The vCenter Server installervalidates that the machine clocks are not more than five minutesapart.
Upgrade requirements: If you upgrade a vCenter Server that is part of a Linked Mode group, it will be removed from the group. After all vCenter Servers in the group are upgraded to version 5.0, you can rejoin them. You cannot join a Linked Mode group during the upgrade procedure when you are upgrading from Virtual Center 25 to vCenter Server 5.0. You can join after the upgrade to vCenter Server is complete.
Domain requirements: If you join a vCenter Server to a standalone instance that is not part of a domain, you must add the standalone instance to a domain and add a domain user as an administrator. To change the domain of a vCenter Server system in a Linked Mode group, isolate the vCenter Server system from the Linked Mode group first.
CAUTION If you need to uninstall and reinstall vCenter Server on more than one member of a Linked Mode group, do so with a single vCenter Server at a time. Uninstalling and reinstalling multiple linked Center Servers at the same time is not supported, and can cause errors that prevent vCenter Server from connecting to vCenter Inventory Service. If it is necessary to uninstall and reinstall multiple linked vCenter Servers at the same time, isolate them from the Linked Mode group first, and rejoin them to the Linked Mode group after the reinstallation is complete.