new vCenter9 Linking

[vmb01]

As stated in this article, "Enhanced Linked Mode* will be deprecated. (When?)

It will be substituted by a new feature called "vCenter Linking!"

My question is: to have the new "vCenter Linking!" feature is necessary to deploy the full VCF stack or vSphere and VCF operations are enough?

[David Nixon]

You don't need to use linking.  The official word is Ops provides the single pane of glass across vCenters.  However, while it is a powerful tool, I find it nowhere as useful as the vSphere client.  Given that vCenters are turning into rabbits (we may be going from 2 to 6 vCenters), I'll probablly leverage linking to make our VM admin's experience match what they are used to.  I'll be using cross vCenter vMotion to get to VCF instead of splitting the existing ELM.

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-FrostByteVA
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[Antoan Arnaudov]

vCenter Enhanced Linked Mode (ELM) was deprecated in vCenter 9.0 but it is still fully functional and supported until removed in a next major vCenter release version.

vCenter ELM was first introduced in vSphere 6.5. It was designed to simplify the management of multiple vCenter server instances by allowing admins to log in to any single instance of vCenter Server and view and manage the inventories of all the vCenter Server systems in the group. In addition, ELM supports replication of licenses, roles, permissions and tags across the linked vCenters.

While ELM did simplify the management of multiple vCenter instances, it also introduced a number of complexities:

• ELM uses synchronous replication technology (not designed for high latency)
• Replication gets out of sync upon failed replication between the ELM nodes.
• Backing up VCs in ELM mode is a manual process which requires downtime and offline snapshots of all vCenters.
• vCenter ELM linking is done during the installation workflow and there is no UI for day-two configurations for linking/unlinking the vCenters.
• Upgrading vCenters in ELM requires downtime (no support for vCenter RDU).
• ELM does not have fine-tune settings about which data to replicate. It always replicates all data across all vCenters in the ring.

Replacement Alternatives

vCloud Foundation (VCF) 9.0 introduces a number of new features which replaces ELM and can be enabled separately or altogether.

The VCF Ops Console UI introduces the following new features:

• License Manager which consolidates the vCenter license management.
• VCF SSO which replaces the legacy ELM SSO across all VCF components.
• vCenter Linking feature which replaces the ELM SPOG features in vSphere H5 client.
• Tags Configuration which supports synchronization of tags across the grouped vCenters.

To use the new vCenter Linking feature first you need to break the vCenters out from their existing ELM configuration. vCenter 9.0 contains a new too designed to break the entire ELM ring altogether:
Deactivate Enhanced Link Mode from vCenter Using the cmsso-util break-elm Utililty

Once the vCenters are broken out of ELM they are ready to be grouped in the new vCenter Linking by using the VCF Ops Admin Console.

The new vCenter Linking features provide the following benefits compared to ELM:

• Enables the same SPOG use cases from the vSphere H5 UI across multiple vCenters as with the legacy ELM.
• Enables admins to add or remove vCenters from a group at any point in time after the initial vCenter installation.
• Uses asynchronous replication technology designed for high latency.
• Grouped vCenters can be backed up without a downtime.
• Upgrading grouped vCenters is compatible with vCenter Reduced Downtime Upgrades (RDU).
• Upgrading multiple grouped vCenters simultaneously is supported.

Independently of vCenter Linking, but only when ELM is disabled, you can configure the new VCF SSO feature:
Configure a New VCF Single Sign-On for a VCF Instance

Finally, for Tags synchronization you could use the new VCF feature:
Tags and Categories Overview

Hope this helps people to migrate from ELM to the new vCenter Linking.