Add a USB drive as the datastore of ESXi 6.5

1. Connect to the ESXi host with SSH
2. Stop the USB arbitrator service. This service is used to passthrough USB device from an ESX/ESXi host to a virtual machine. (When disabling it, you can no longer passthrough USB devices to VMs)

   ~ # /etc/init.d/usbarbitrator stop

3. (optional) Use this command to permanently disable the USB arbitrator service after reboot.

   ~ # chkconfig usbarbitrator off

4. Plug in the USB device to your ESXi host. While connecting the USB device you can either watch /var/log/vmkernel.log to identify the device name or identify it within /dev/disks.
   Devices are either named mpx.vmhbaXX or with an naa.X number.

   ~ # ls /dev/disks/

5. Write a GPT label to the device (Assuming that the Device ID is naa.5000000000000001)

   ~ # partedUtil mklabel /dev/disks/naa.5000000000000001 gpt

6. To create a partition you need to know the start sector, end sector, which depends on the device size and the GUID.
   The start sector is always 2048
   The GUID for VMFS is AA31E02A400F11DB9590000C2911D1B8
   The end sector can be calculated with the following formula (Use the numbers from getptbl):

   ~ # partedUtil getptbl /dev/disks/naa.5000000000000001
   gpt
   15566 255 63 250069680

   15566 * 255 * 63 - 1 = 250067789
   You can also calculate the end sector with the following command:

   ~ # eval expr $(partedUtil getptbl /dev/disks/naa.5000000000000001 | tail -1 | awk '{print $1 " \\* " $2 " \\* " $3}') - 1
   250067789

7. Create the VMFS partition (Replace with your end sector)

   ~ # partedUtil setptbl /dev/disks/naa.5000000000000001 gpt "1 2048 250067789 AA31E02A400F11DB9590000C2911D1B8 0"

8. Format the partition with VMFS5 or VMFS6

   # VMFS v5
   ~ # vmkfstools -C vmfs5 -S USB-Datastore /dev/disks/naa.5000000000000001:1
   
   # VMFS v6
   ~ # vmkfstools -C vmfs6 -S USB-Datastore /dev/disks/naa.5000000000000001:1

The USB-Datastore should now appear in your datastores view.

This is how your command output should look like:

[root@esx4:~] partedUtil mklabel /dev/disks/naa.5000000000000001 gpt
[root@esx4:~] eval expr $(partedUtil getptbl /dev/disks/naa.5000000000000001 | tail -1 | awk '{print $1 " \\* " $2 " \\* " $3}') - 1
250067789
[root@esx4:~] partedUtil setptbl /dev/disks/naa.5000000000000001 gpt "1 2048 250067789 AA31E02A400F11DB9590000C2911D1B8 0"
gpt
0 0 0 0
1 2048 250067789 AA31E02A400F11DB9590000C2911D1B8 0
[root@esx4:~] vmkfstools -C vmfs6 -S USB-Datastore /dev/disks/naa.5000000000000001:1
create fs deviceName:'/dev/disks/naa.5000000000000001:1', fsShortName:'vmfs6', fsName:'USB-Datastore'
deviceFullPath:/dev/disks/naa.5000000000000001:1 deviceFile:naa.5000000000000001:1
ATS on device /dev/disks/naa.5000000000000001:1: not supported
.
Checking if remote hosts are using this device as a valid file system. This may take a few seconds...
Scanning for VMFS-3/VMFS-5 host activity (512 bytes/HB, 2048 HBs).
Creating vmfs6 file system on "naa.5000000000000001:1" with blockSize 1048576, unmapGranularity 1048576, unmapPriority default and volume label "USB-Datastore".
Successfully created new volume: 583b0efb-33b7ba1e-57e7-001fc69b9659