Creating a VMFS datastore greater than 2TB on a USB device in ESXi

I recently had an inquiry from one of our Technical Account Managers (TAM) with an interesting question from their customer. They were looking to manually migrate VMs from one environment to another and because these were isolated and secured environments, they were looking to use an encrypted USB device that would be formatted with VMFS. While researching this topic, they came across several mentions in the community that VMFS on USB has a 2TB limitation, which was not going to work for them.

I personally have never tried nor had the need to ever create a VMFS datastore that was greater than 2TB on a USB device, but I have certainly heard simliar claims in the past and this finally piqued my interests. I reached out to a few folks within VMware Engineering that works on our USB stack and came to learn that is no such limitation when using VMFS on USB. In fact, they also pointed out that some of the reported errors in the community was most likely due to hardware issues rather than capacity of the underlying USB device. This was actually great news and of course I wanted to verify for myself before replying back.

First off, VMFS on USB is NOT officially supported by VMware, so I just want to make sure that is clear. With that said, this is a fairly common practice within the community, especially for VMware Homelabs which I have also demonstrated this capability as early as 2011 and most recently in 2015 for use with vSAN and in 2020 for a vSAN Witness with ESXi on Arm. While most USB storage devices, especially those found in the consumer space are not durable enough for Enterprise usage, it does NOT mean you can not have a reliable USB storage device. I actually wrote about this topic a few years back where you can use inexpensive M.2 enclosures to house an NVMe device that can then be connected via USB/USB-C to have a more reliable storage medium that can also be cost effective.

I was able to get a hold of a 4TB USB storage device and using the following instructions, which have been confirmed by Engineering, I was successful in creating a VMFS datastore that was greater than 2TB running on a USB device using ESXi 7.0 (GA) as well as the latest ESXi 7.0 Update 3c release.

Step 1 - Identify the specific USB storage device that you wish to use for your VMFS datastore, so that we can disable this specific USB device from passthrough. This is handy because you may not want to completely disable USB passthrough for other USB devices and previously, the only method was disabling the USB Arbitrator service in ESXi, which was not ideal.

esxcli hardware usb passthrough device list

Make a note of the Bus, Dev, VendorID and ProductID for the USB device that you wish to disable passthrough for.

Step 2 - Run the following ESXCLI command and replace the Bus, Dev, VendorID and ProductID with the values from Step 1 to disable passthrough for the USB device so that ESXi can now claim it.

esxcli hardware usb passthrough device disable -d 2:5:1058:2621

Step 3 - Next, we need to identify the device name for our USB device which should be in the form of "mpx.vmhbaX:CX:TX:LX". To do so, run the following command and if you have multiple USB storage devices, you can refer to the Size column to confirm you have found the correct device.

vdq -q

Step 4 - Replace the DEVICE_PATH variable with the name of the USB storage device and run the following 5 command which will partition and automatically create a VMFS 6 datastore using the entire device.

DEVICE_PATH="/vmfs/devices/disks/mpx.vmhba32:C0:T0:L0"

partedUtil mklabel ${DEVICE_PATH} msdos

END_SECTOR=$(eval expr $(partedUtil getptbl ${DEVICE_PATH} | tail -1 | awk '{print $1 " \\* " $2 " \\* " $3}') - 1)

/sbin/partedUtil "setptbl" "${DEVICE_PATH}" "gpt" "1 2048 ${END_SECTOR} AA31E02A400F11DB9590000C2911D1B8 0"

/sbin/vmkfstools -C vmfs6 -b 1m -S usb-datastore ${DEVICE_PATH}:1

Once the operation has successfully completed, you can now navigate to your vSphere Client or ESXi Embedded Host Client (if you do not have vCenter Server) and you should be able to see our newly created VMFS datastore!