Architecting a vCloud Availability for vCloud Director Solution : vCloud Availability Architecture Design Overview
   
vCloud Availability Architecture Design Overview
3.1 vCloud Availability Architecture
VMware vSphere Replication is the underlying replication technology that is used by vCloud Availability for vCloud Director. vSphere Replication provides a hypervisor-based, asynchronous replication of virtual machines, independent from the underlying storage hardware, which is essential for replications to and from the public cloud with disparate hardware used.
The vSphere Replication Agent is built into the VMware ESXi™ hypervisor, and with the help of the vSCSI filter, tracks block changes to virtual disks (VMDKs) of running virtual machines. Depending on the required RPO, the hypervisor then transmits the changed blocks in regular intervals to the target environment.
The following figure shows the components that comprise vCloud Availability for vCloud Director.
Figure 1. vCloud Availability for vCloud Director Component Diagram
 
Table 1. Components
Component
Description
VMware vCloud Director
Existing vCloud Director components consisting of multiple vCloud Director cells, vCloud Director database (VCD-SP DB), and vSphere (vCenter Server, ESXi hosts, datastores) and VMware NSX® resources.
RabbitMQ
AMQP message broker that provides communication between vCloud Director and the other components that extend vCloud Director functionality.
vSphere Replication Cloud Service
Tenant-aware replication manager that extends vCloud API with vCloud Availability for vCloud Director APIs and manages replications and failovers.
Cassandra
Cassandra noSQL database cluster used for VM performance metrics and for replication metadata, and for configuration of vCloud Availability for vCloud Director infrastructure components.
Cloud Proxy Cells
vCloud Director cell-like components whose purpose is to tunnel replicated traffic to and from the cloud and establish control connections with on-premises vSphere Replication Appliance.
vCloud Availability Portal
Appliances that provide a tenant-level UI portal to manage replications in the cloud.
vSphere Replication Manager Server
Management component that manages the replication process of tenant virtual machines. It has a 1:1 relationship with the cloud resource VMware vCenter Server® instances.
vSphere Replication Server
Replication server that receives the replication data and records the changes for each replicated virtual machine. It has a 1:many relationship with cloud resource vCenter Server instances.
vSphere Replication Appliance
On-premises vSphere Replication component that combines both manager and replication server functionality. It also contains the vCloud Tunneling Agent that terminates the to-cloud and from-cloud replication tunnels. vSphere Replication Appliance can be extended with deployment of additional vSphere Replication Server instances for scale.
VMware Platform Services Controller™
An external Platform Services Controller runs the lookup service necessary for discovery of vCloud Availability components (Cassandra nodes, vSphere Replication Manager Server, and vSphere Replication Cloud Service) and provides secure token service to authenticate replication solution users to vCloud Director.