Slow reboot times of virtual machines after mounting Persistent Memory (PMem) NVDIMM devices

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Rebooting a virtual machine that has NVDIMM devices takes significantly longer than expected
• Adding additional NVDIMM devices makes the reboot times longer again
• When the NVDIMM devices are removed the virtual machine boots quickly

Environment

VMware vSphere ESXi 6.7

Cause

During a reboot of the virtual machine numerous cache flushes are performed on all pmem regions. This causes a delay in the reboot times.

Resolution

VMware is aware of this issue and working to resolve it in a future release.

Workaround:

To workaround the issue a power off / power on can be performed as opposed to a reboot. During a power off / power on cycle the slow cache flushes are not performed. 

Note: Care should be taken by the administrator to ensure applications at the operating system layer are manually shutdown first before implementing the workaround.