This section provides an architecture overview and guidance on managing and scaling a Citrix Virtual Apps and Desktops environment on Dell EMC VxRail appliances.
The following figure depicts the architecture of the validated solution, including the network, compute, management, and storage layers.
The deployment option for this Dell EMC Ready System for VDI uses Citrix Machine Creation Services (MCS) with a random or non-persistent desktop—that is, virtual desktops are assigned randomly as users connect. When users log off, changes they made are discarded. The desktop is reset to its original state and is available for another user to log in and use.
vSAN-based appliances solutions provide flexibility as you scale, reducing the initial and future cost of ownership. Add additional physical and virtual servers to the server pools to scale horizontally. Add virtual resources to the infrastructure to scale vertically.
Each component of the solution architecture scales independently depending on the required number of supported users. You can add appliance nodes at any time to expand the vSAN SDS pool in a modular fashion. The scaling limit for vSAN is restricted by the limits of the hypervisor at 64 nodes per block.
The recommended limit of linked clones per cluster is 4,000.
Each instance of VMware vCenter can service a maximum of 4,000 linked or full clone virtual machines. A Citrix "pod architecture" consists of a virtual desktop "site" and one or more "zones" at each site. The following figure shows a 4,000-user MCS linked clone/vSAN configuration, which equates to a single zone within a site.
The following figure shows a scale-out of 20,000 MCS linked-clone VMs with vSAN. The recommended limit for a zone is 10,000 sessions. In this example, there are two sites with three zones each. The sites are load-balanced and presented to the users as a single entity.
Dell EMC 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.
Citrix VDI Handbook and Best Practices provides more information about Citrix best practices for scaling.
The compute, management, and storage layers are converged into a single VxRail Appliance or vSAN Ready Nodes block, hosting VMware vSphere. The number of nodes that are supported for vSphere 6.5 or 6.7, which is 64, determines the recommended boundaries of an individual vSphere cluster.
Dell EMC recommends that the VDI management infrastructure nodes be separated from the compute resources. Because our test environment was small, both management and compute are in the same vSphere HA cluster. Optionally, the management node can also be used for VDI VMs with an expected reduction of 30 percent of host resources for these nodes only. The 30 percent accounts for management VM resource reservations and should be factored in when sizing.
Compute hosts can be used interchangeably for Citrix Virtual Apps hosted applications and desktops, as required.