Enhanced Linked Mode (ELM) is the vCenter Server feature designed to connect multiple vCenter Server instances. When configured, ELM allows an administrator to log in to any of the linked vCenter Servers and view and manage the inventories (such as hosts, virtual machines, and clusters) of all connected vCenter Servers from a single vSphere Client session. This provides a unified management pane across different sites or vCenter instances, directly addressing the administrator's requirement to manage both Site A and Site B from one interface.

A. VMware Certificate Authority: This component manages security certificates for vSphere components but does not provide a unified management interface for multiple vCenter inventories.

B. VMware Site Recovery Manager: This is a disaster recovery and business continuity solution used to orchestrate failover between sites, not for unified day-to-day inventory management.

C. vCenter Single Sign-On: This provides authentication services, allowing a user to log in once. While a prerequisite for ELM, it is the authentication mechanism, not the feature that links the inventories.

1. VMware vSphere Product Documentation

vCenter Server and Host Management (vSphere 8.0).

Section: "vCenter Enhanced Linked Mode"

Content: "vCenter Enhanced Linked Mode allows you 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. You can join up to 15 vCenter Server appliance deployments with vCenter Enhanced Linked Mode in a single vSphere Single Sign-On domain." This directly confirms that ELM provides the single-pane-of-glass management required by the question.

2. VMware vSphere Product Documentation

vSphere Installation and Setup (vSphere 8.0).

Section: "vSphere Authentication"

Content: "vCenter Single Sign-On is an authentication broker and security token exchange infrastructure... When you install vCenter Server

you deploy a vCenter Single Sign-On server." This reference clarifies that SSO's role is authentication

distinguishing it from the management linking function of ELM.

3. VMware vSphere Product Documentation

Site Recovery Manager Administration (Version 8.7).

Section: "Introduction to Site Recovery Manager"

Content: "VMware Site Recovery Manager is a business continuity and disaster recovery solution that helps you to plan

test

and run the recovery of virtual machines between a protected vCenter Server site and a recovery vCenter Server site." This defines SRM's purpose as disaster recovery

not unified management.