How to Create VMFS Datastore on Vmware OS bootdrive

Normally a vmfs partition is already created by ESXi on the boot drive. You can verify by going logging into the ESX Web GUI and navigating to Storage --> Devices --> Boot disk (Figure 1).

Figure 1

Clicking on the drive will show the Partition diagram of the boot drive and the vmfs partition is usually partition 3. Make a note of the UUID of the device and the partition number (Figure 2).

Figure 2

Create a vmfs datastore named datastore-ssd on the the boot device using the UUID and the partition number you noted above using the command below (Device format is /vmfs/devices/disks/ vm1.<UUID>:3):

vmkfstools --createfs vmfs6 -S datastore-ssd /vmfs/devices/disks/vml.0100000000453530465f314634345f344134345f314230300057444320434c:3

If successful, you should get an output similar to below:

create fs deviceName:'/vmfs/devices/disks/vml.0100000000453530465f314634345f344134345f314230300057444320434c:3', fsShortName:'vmfs6', fsName:'datastore-ssd'
deviceFullPath:/dev/disks/t10.NVMe____WDC_CL_SN720_SDAQNTW2D512G2D2000__________E50F1F444A441B00:3 deviceFile:t10.NVMe____WDC_CL_SN720_SDAQNTW2D512G2D2000__________E50F1F444A441B00:3
ATS on device /dev/disks/t10.NVMe____WDC_CL_SN720_SDAQNTW2D512G2D2000__________E50F1F444A441B00:3: not supported
.
Checking if remote hosts are using this device as a valid file system. This may take a few seconds...
Scanning for VMFS-6 host activity (4096 bytes/HB, 1024 HBs).
Creating vmfs6 file system on "t10.NVMe____WDC_CL_SN720_SDAQNTW2D512G2D2000__________E50F1F444A441B00:3" with blockSize 1048576, unmapGranularity 1048576, unmapPriority default and volume label "datastore-ssd".
Successfully created new volume: 5fc102ac-257939bc-7e5b-0cc47ac8166c

Additionally, the datastore you created should appear under Storage --> Datastores in your ESXi Web Gui (Figure 3).

Figure 3