Why use the VMware vCenter Server Appliance (vCSA)

Installing vCenter server has come a long way since the early days of building and configuring a Windows server. Most of the issues I recall were around databases, either running out of space when using SQL express or remembering to configure the ODBC settings before installing vCenter.  Fortunately, things have moved on since then and almost all deployments we complete here at ComputerWorld now use the vCenter Server Appliance. This is a preconfigured virtual appliance running Linux (Project Photon OS) that has been optimised specifically for vCenter services. The appliance can be deployed in several different sizes (depending on the number of hosts or virtual machines you need to support) and uses an embedded vpostgres database. In terms of scale it can support anything up to 2000 hosts or 35000 virtual machines per appliance. If you’re still attached to the Windows version of vCenter then it’s worth noting the next version of vSphere will be the last release of the Windows version.


vCenter Components

Just to recap vSphere 6 introduced the Platform Services Controller (PSC) component of vCenter that enhanced the Single Sign-on role found in 5.5 and adding some additional services. You can choose to deploy both components to the same server or split them out if required but more on this later. The list below shows a breakdown of the services are installed to each vCenter component.


  • Single Sign-On
  • vSphere License Service
  • VMware Certificate Authority

vCenter Server

  • vCenter Inventory Service
  • PostgresSQL
  • vSphere Web Client
  • vSphere Client (HTML 5)
  • vSphere ESXi Dump Collector
  • VMware Syslog Collector
  • vSphere Auto Deploy
  • VMware vSphere Update Manager Extension

A full explanation of the roles above can be found in the documentation centre.


Many VMware products are now based on appliances running Photon OS and deploying vCenter into your environment with this approach has the following benefits;

  • The upgrade process is far simpler and quicker using the management interface (as shown below).
  • There is a built-in file backup feature to protect to config (it doesn’t yet have a scheduling function)
  • It’s one less Windows server to manage, license and patch.
  • vSphere updated manager (VUM) is fully integrated.

vCenter Topologies

There are several supported deployment topologies that are supported by VMware ranging from a single server to multiple servers across many sites. Full details on supported topologies can be found in the following KB article.


The simplest deployment option is the “vCenter Server with an Embedded Platform Services Controller” and as you can probably guess means the Platform Services Controller (PSC) and vCenter Server components are integrated on a single appliance. This is usually fine for small deployments in a single site and if licensed you can easily take advantage of the built in HA functionality. There are some limitations with this deployment model in that it doesn’t support Enhanced Link Mode (ELM) in versions prior to 6.7 and it doesn’t support PSC replication.


If you have multiple sites, or multiple vCenter servers then Enhanced Linked Mode (ELM) allows up to 15 vCenter servers to be managed centrally with vSphere 6.5. To support ELM in versions prior to 6.7, you need to choose the “vCenter Server with an External Platform Services Controller” option. This method allows you to deploy an appliance with just the PSC components, then you deploy a further appliance with just the vCenter components and link it to the previously configured PSC. One thing worth noting that it is possible to migrate from an embedded PSC to an external PSC if your requirements change. When scaling out vCenter components it’s also important to consider high availability and resilience requirements when planning these types of deployments. VMware have a ton of resources on vCenter deployments and configurations on their vSphere Central site which also has some nice feature walkthroughs.


In my lab I’ve chosen to deploy a vCenter Server with an External Platform Services controller as I have two sites that I wish to manage centrally. I also plan to implement and test cross-vCenter NSX which requires two vCenter servers. The next couple of posts will run through the installation process of deploying vCenter Server with an External Platform Services Controller.

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