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.