When determining the compute capacity for a VMware Cloud Foundation (VCF) VI Workload Domain, the goal is to calculate the usable resources available to support virtual machines (VMs) and their workloads. This involves evaluating the physical compute resources (CPU, memory, storage) and accounting for overheads, efficiency features, and configurations that impact resource availability. Below, each option is analyzed in the context of VCF 5.2, with a focus on official documentation and architectural considerations:

A. vSAN space efficiency feature enablementThis is a critical element to consider. VMware Cloud Foundation often uses vSAN as the primary storage for VI Workload Domains. vSAN offers space efficiency features such as deduplication, compression, and erasure coding (RAID-5/6). When enabled, these features reduce the physical storage capacity required for VM data, directly impacting the usable storage resources available for compute workloads. For example, deduplication and compression can significantly increase usable capacity by eliminating redundant data, while erasure coding trades off some capacity for fault tolerance. The VMware Cloud Foundation 5.2 Planning and Preparation documentation emphasizes the need to account for vSAN policies and efficiency features when sizing storage, as they influence the effective capacity available for VMs. Thus, this is a key factor in compute capacity planning.

B. VM swap fileThe VM swap file is an essential consideration for compute capacity, particularly for memory resources. In VMware vSphere (a core component of VCF), each powered-on VM requires a swap file equal to thesize of its configured memory minus any memory reservation. This swap file is stored on the datastore (often vSAN in VCF) and consumes storage capacity. When calculating usable resources, you must account for this overhead, as it reduces the available storage for other VM data (e.g., virtual disks). Additionally, if memory overcommitment is used, the swap file size can significantly impact capacity planning. The VMware Cloud Foundation Design Guide and vSphere documentation highlight the importance of factoring in VM swap file overhead when determining resource availability, making this a valid element to consider.

C. Disk capacity per VMWhile disk capacity per VM is important for storage sizing, it is not directly a primary factor in calculatingusable compute resourcesfor a VI Workload Domain in the context of this question. Disk capacity per VM is a workload-specific requirement that contributes to overall storage demand, but it does not inherently determine the usable CPU or memory resources of the domain. In VCF, storage capacity is typically managed by vSAN or other supported storage solutions, and while it must be sufficient to accommodate all VMs, it is a secondary consideration compared to CPU, memory, and efficiency features when focusing on compute capacity. Official documentation, such as the VCF 5.2 Administration Guide, separates storage sizing from compute resource planning, so this is not one of the top three elements here.

D. Number of 10GbE NICs per VMThe number of 10GbE NICs per VM relates to networking configuration rather than compute capacity (CPU and memory resources). While networking is crucial for VM performance and connectivity in a VI Workload Domain, it does not directly influence the calculation of usable compute resources like CPU cores or memory. In VCF 5.2, networking design (e.g., NSX or vSphere networking) ensures sufficient bandwidth and NICs at the host level, but per-VM NIC counts are a design detail rather than a capacity determinant. The VMware Cloud Foundation Design Guide focuses NIC considerations on host-level design, not VM-level compute capacity, so this is not a relevant element here.

E. CPU/Cores per VMThis is a fundamental element in compute capacity planning. The number of CPU cores assigned to each VM directly affects how many VMs can be supported by the physical CPU resources in the VI Workload Domain. In VCF, compute capacity is based on the total number of physical CPU cores across all ESXi hosts, with a minimum of 16 cores per CPU required for licensing (as per the VCF 5.2 Release Notes and licensing documentation). When calculating usable resources, you must consider how many cores are allocated per VM, factoring in overcommitment ratios and workload demands. The VCF Planning and Preparation Workbook explicitly includes CPU/core allocation as a key input for sizing compute resources, making this a critical factor.

F. Number of VMsWhile the total number of VMs is a key input for overall capacity planning, it is not a direct element in calculatingusable compute resources. Instead, it is a derived outcome based on the available CPU, memory, and storage resources after accounting for overheads and per-VM allocations. The VMware Cloud Foundation 5.2 documentation (e.g., Capacity Planning for Management and Workload Domains) uses the number of VMs as a planning target, not a determinant of usable capacity. Thus, it is not one of the top three elements for this specific calculation.

Conclusion:The three elements that should be considered when calculating usable compute resources arevSAN space efficiency feature enablement (A),VM swap file (B), andCPU/Cores per VM (E). These directly impact the effective CPU, memory, and storage resources available for VMs in a VI Workload Domain.

References:

VMware Cloud Foundation 5.2 Planning and Preparation Workbook

VMware Cloud Foundation 5.2 Design Guide

VMware Cloud Foundation 5.2 Release Notes

VMware vSphere 8.0 Update 3 Documentation (for VM swap file and CPU allocation details)

VMware Cloud Foundation Administration Guide