The customer reports a severe drop in CPU availability on their ESXi hosts while performing a Dell iDRAC firmware update, despite active CPU demand from running virtual machines.

Products

• VMware vSphere ESXi

Issue/Introduction

The CPU availability plummets at the hypervisor level, directly degrading virtual machine performance and causing resource contention. A reboot of the affected ESXi host successfully restores normal CPU availability.

Environment

ESXi 8.0.3 - Build (25067014) 8.0U3h
This issue is specific to iDRAC 1.30.10.51,

Cause

The root cause is isolated to a third-party hardware/firmware behavior, specifically tied to the Dell iDRAC version 1.30.10.51 update process.

Resolution

Because the CPU throttling is being enforced entirely at the physical hardware/BIOS level by the Dell iDRAC, ESXi has no software mechanism to override it. Resolving the root cause requires Dell Engineering to investigate the iDRAC firmware payload (1.30.10.51) and provide a mitigation to prevent the baseboard controller from locking the CPUs during the flash process.