The remediation pre-check report shows the results of a check that is performed on a cluster or a host before remediation. During that check, vSphere Lifecycle Manager identifies possible issues that might prevent successful remediation. Depending on the type of issue, vSphere Lifecycle Manager suggests actions that you must take to fix the issue or resolves the issue automatically.

You can generate a pre-check remediation report in the vSphere Lifecycle Manager compliance view for an object.

Table 1. Cluster Issues
Current Configuration/Issue Recommended Action Details
DRS is disabled on the cluster. Enable DRS on the cluster. DRS enables vCenter Server to place and migrate virtual machines automatically on hosts to attain the best use of cluster resources.
vSAN health check fails during the pre-check. Navigate to the vSAN Health page and address any health issues before proceeding with remediation. The vSAN health check performs a series of tests on the hosts in the vSAN cluster. The vSAN health check must succeed to ensure the hosts are successfully remediated. If you start a remediation task in a vSAN cluster that failed the vSAN health check during the remediation pre-check, the hosts enter maintenance mode, get upgraded, but might fail to exit maintenance mode. The remediation eventually fails.
Insufficient licenses for one or multiple ESXi hosts in the cluster. Ensure that you have multiple licenses for the ESXi hosts that have more than 32 cores per CPU. Starting with vSphere 7.0, one CPU license covers up to 32 physical cores. If a CPU has more than 32 cores, you must assign additional CPU licenses to the respective ESXi host. For more information, see https://www.vmware.com/company/news/updates/cpu-pricing-model-update-feb-2020.html.
DPM is enabled on the cluster. None.

vSphere Lifecycle Manager disables DPM automatically.

If a host has no running virtual machines, DPM might put the host in standby mode before or during remediation and vSphere Lifecycle Manager cannot remediate them.
HA admission control is enabled on the cluster. None.

vSphere Lifecycle Manager disables HA admission control automatically.

HA admission control prevents the migration of virtual machines with vSphere vMotion and the hosts cannot enter maintenance mode.
Table 2. Host Issues
Current Configuration/Issue Recommended Action Details
A CD/DVD drive is attached to a virtual machine on the ESXi host. Disconnect the CD/DVD drive. Any CD/DVD drives or removable devices connected to the virtual machines on a host might prevent the host from entering maintenance mode. When you start a remediation operation, the hosts with virtual machines to which removable devices are connected are not remediated.
A floppy drive is attached to a virtual machine on the ESXi host. Disconnect the floppy drive. Any floppy drives or removable devices connected to the virtual machines on a host might prevent the host from entering maintenance mode. When you start a remediation operation, the hosts with virtual machines to which removable devices are connected are not remediated.
Fault Tolerance (FT) is enabled for a virtual machine on the ESXi host. Disable FT for the virtual machine. If FT is enabled for any of the virtual machines on a host, vSphere Lifecycle Manager cannot remediate that host.
A powered on virtual machine is configured to use Virtual Flash Read Cache. "Disable Virtual Flash Read Cache before proceeding with the upgrade. Starting with vSphere 7.0, Virtual Flash Read Cache is not supported. During an upgrade operation, vSphere Lifecycle Manager removes Virtual Flash Read Cache for all virtual machines on the host. Before remediation, consult https://kb.vmware.com/s/article/2057840.
VMware vCenter Server is installed on a virtual machine on the ESXi host and DRS is disabled on the cluster. Enable DRS on the cluster and ensure that virtual machines can be migrated with vSphere vMotion. One of the virtual machines in the cluster runs the vCenter Server instance that you currently use. If you enable DRS on the cluster, vSphere vMotion can migrate the virtual machine where vCenter Server runs to ensure that the remediation of the hosts is successful.
An ESXi host in the cluster has a CPU wih more than 32 cores and requires multiple licenses. Assign as many licenses as the host needs. Starting with vSphere 7.0, one CPU license covers up to 32 physical cores. If a CPU has more than 32 cores, you must obtain additional CPU licenses. For more information, see https://www.vmware.com/company/news/updates/cpu-pricing-model-update-feb-2020.html.