The requirement is to reduce network latency between two application virtual machines (VMs) in a VMware Cloud Foundation (VCF) 5.2 SDDC environment. Network latency is influenced by the physical distance and network hops between VMs. In a vSphere environment (core to VCF), VMs on the same ESXi host communicate via the host’s virtual switch (vSwitch or vDS), avoiding physical network traversal, which minimizes latency. Let’s evaluate each option:
Option A: Configure a Storage DRS rule to keep the application virtual machines on the same datastoreStorage DRS manages datastore usage and VM placement based on storage I/O and capacity, not network latency. ThevSphere Resource Management Guidenotes that Storage DRS rules (e.g., VMaffinity) affect storage location, not host placement. Two VMs on the same datastore could still reside on different hosts, requiring network communication over physical links (e.g., 10GbE), which doesn’t inherently reduce latency.
Option B: Configure a DRS rule to keep the application virtual machines on the same ESXi hostDRS (Distributed Resource Scheduler) controls VM placement across hosts for load balancing and can enforce affinity rules. A “keep together” affinity rule ensures the two VMs run on the same ESXi host, where communication occurs via the host’s internal vSwitch, bypassing physical network latency (typically <1µs vs. milliseconds over a LAN). TheVCF 5.2 Architectural GuideandvSphere Resource Management Guiderecommend this for latency-sensitive applications, directly meeting the requirement.
Option C: Configure a DRS rule to separate the application virtual machines to different ESXi hostsA DRS anti-affinity rule forces VMs onto different hosts, increasing network latency as traffic must traverse the physical network (e.g., switches, routers). This contradicts the goal of reducing latency, making it unsuitable.
Option D: Configure a Storage DRS rule to keep the application virtual machines on different datastoresA Storage DRS anti-affinity rule separates VMs across datastores, but this affects storage placement, not host location. VMs on different datastores could still be on different hosts, increasing network latency over physical links. This doesn’t address the requirement, per thevSphere Resource Management Guide.
Conclusion:Option B is the correct design decision. A DRS affinity rule ensures the VMs share the same host, minimizing network latency by leveraging intra-host communication, aligning with VCF 5.2 best practices for latency-sensitive workloads.References:
VMware Cloud Foundation 5.2 Architectural Guide(docs.vmware.com): Section on DRS and Workload Placement.
vSphere Resource Management Guide(docs.vmware.com): DRS Affinity Rules and Network Latency Considerations.
VMware Cloud Foundation 5.2 Administration Guide(docs.vmware.com): SDDC Design for Performance.
