The physical design specifications of the ESXi host determine the characteristics of the ESXi hosts that you use to deploy this VMware Validated Design.

Physical Design Specification Fundamentals

The configuration and assembly process for each system is standardized, with all components installed in the same manner on each ESXi host. Because standardization of the physical configuration of the ESXi hosts removes variability, you operate an easily manageable and supportable infrastructure. Deploy ESXi hosts with identical configuration across all cluster members, including storage and networking configurations. For example, consistent PCI card slot placement, especially for network controllers, is essential for accurate alignment of physical to virtual I/O resources. By using identical configurations, you have an even balance of virtual machine storage components across storage and compute resources.

Select all ESXi host hardware, including CPUs, according to VMware Compatibility Guide.

The sizing of physical servers that run ESXi requires special considerations when you use vSAN storage. The design provides details on using vSAN as the primary storage system for the management cluster and the shared edge and compute cluster. This design also uses vSAN ReadyNodes. For information about the models of the physical servers, see the vSAN ReadyNode compatibility guide.

This design supports using a storage system other than vSAN as the primary storage system for the management and shared edge and compute clusters. However, using a non-vSAN storage is not a part of the documentation of this validated design. For details on vSAN capacity and performance characteristics to aid your selection of non-vSAN storage, see Physical Storage Design.

  • An average-size VM has two vCPUs with 4 GB of RAM.
  • A standard 2U server can host 60 average-size VMs on a single ESXi host.
Table 1. Design Decisions on the Physical Design of the ESXi Hosts

Decision ID

Design Decision

Design Justification

Design Implication

SDDC-PHY-009

Use vSAN ReadyNodes with vSAN storage.

Using vSAN ReadyNodes ensures full compatibility with vSAN at deployment.

Hardware choices might be limited.

SDDC-PHY-010

Verify that all nodes have uniform configuration across a cluster.

A balanced cluster has more predictable performance even during hardware failures. In addition, the impact on performance during resync or rebuild is minimal if the cluster is balanced.

Apply vendor sourcing, budgeting, and procurement considerations for uniform server nodes, on a per cluster basis.

ESXi Host Memory

The amount of memory required for compute clusters varies according to the workloads running in the cluster. When sizing memory for compute cluster hosts, consider the admission control setting (n+1), which reserves the resources of one host for failover or maintenance.

The number of disk groups and disks that an ESXi host manages determines the memory requirements. To support the maximum number of disk groups, you must provide 32 GB of RAM. For more information about disk groups, including design and sizing guidance, see Administering VMware vSAN from the vSphere documentation.

Table 2. Design Decisions on the ESXi Host Memory

Decision ID

Design Decision

Design Justification

Design Implication

SDDC-PHY-011

Set up each ESXi host in the management cluster with a minimum of 256 GB RAM.

The management and edge VMs in this cluster require a total of 453 GB RAM.

The remaining RAM is available for new capabilities of the SDDC such as deployment of VMware NSX-T or VMware PKS.

In a four-node cluster, only 768 GB is available for use due to the n+1 vSphere HA setting.

ESXi Host Boot Device

Minimum boot disk size for ESXi in SCSI-based devices (SAS, SATA, or SAN) is greater than 5 GB. ESXi can be deployed using stateful local SAN SCSI boot devices, or by using vSphere Auto Deploy.

Selecting a boot device type and size for vSAN has the following considerations:

  • vSAN does not support stateless vSphere Auto Deploy.
  • Device types as ESXi boot devices
    • USB or SD embedded devices. The USB or SD flash drive must be at least 4 GB.
    • SATADOM devices. The size of the boot device per host must be at least 16 GB.
See VMware vSAN Design and Sizing Guide to select the option that best fits your hardware.