VMware vSAN based solutions provide flexibility as you scale, reducing the initial and future cost of ownership. Add physical and virtual servers to the server pools to scale horizontally (scaling out). Add virtual resources to the infrastructure to scale vertically (scaling up).
Each component of the solution architecture scales independently based on the required number of supported users. You can add appliance nodes at any time to expand the vSAN Software Defined Storage (SDS) pool in a modular fashion. The scaling limit for vSAN is restricted by the limits of the hypervisor to 64 nodes per block.
The recommended limit of linked clones per cluster is 5,000.
For the latest sizing guidance, see the VMware Configuration Maximums and Citrix Virtual Apps and Desktops 7 2012 documentation.
This reference architecture uses MCS linked clones within a Citrix pod architecture, as shown in the following figures. A Citrix pod architecture consists of a virtual desktop site and one or more zones at each site. Each instance of VMware vCenter can service a maximum of 40,000 powered-on virtual machines. However, additional design considerations typically limit this number. The limit for Citrix pod architecture with the LHC feature enabled is currently 10,000 VDAs per zone and 40,000 VDAs per site.
We used design limits of 5,000 MCS linked clone VMs per zone and up to 10,000 VMs per pod.
The following figure shows a 5,000-user MCS linked clone configuration that is based on a 200-user per node density, which equates to a single zone within a site.
Alternative architectures such as a combined management and compute architecture can also be used, which would eliminate the need for a separate management cluster. In this configuration, each pod contains its own vCenter Server instance and VDI components.
The following figure shows a scale-out to a 20,000-user Citrix Virtual Apps and Desktops vSAN Pod with 5,000-user zones. In this example, there are two sites with four zones, which can be load-balanced and presented to users as a single entity.
Dell Technologies recommends a validated disk configuration for general-purpose VDI. These configurations leave drive slots available for future vertical expansion and ensure that you protect your investment as new technology transforms your organization.
For more information about Citrix best practices for scaling, see the Citrix VDI Handbook and Best Practices.