It is not uncommon, especially in troubleshooting scenarios where you might find yourself needing to transfer files to or from an ESXi host using a USB device as it may not be reachable on the network. Another common case for directly attaching a USB device to an ESXi host is to transfer a large amount of Virtual Machines that were exported from another system and rather than streaming the content from your desktop, you may want to connect it directly to ESXi host. In fact, I had this very use case when I was a customer after we had acquired a company and needed to transfer their assets to our infrastructure. The IT admins just copied everything onto a USB device and then shipped us the drive for processing.
Historically, it was understood that ESXi could only access a USB device (requires disabling the USB arbitrator service) if it contains a FAT16 partition which are then automatically mounted under the /vmfs/volumes/ path. The biggest issue with FAT16 is that the size of the partition has to be <=2GB which severely limits its use for larger files. Another alternative that came up in recent years years is that you could run VMFS on a USB device, but that obviously would require you to format the USB device with VMFS and it would only be readable between ESXi hosts. If you were looking for something more generic like FAT32 which supports a larger partition size, it was assumed this was not possible, at least I was under that impression.
It was only recently as part of a project I had been working on where I was re-visiting this topic that I had discovered that other partition types such as FAT32 and even NTFS from a USB device could actually be accessed by ESXi 6.x. The assumption that I and probably others had made was that just because the partitions were not visible or mounted by ESXi, it does not mean the underlying USB device would also not be accessible. To access a FAT32 partition from a USB device in ESXi, you can use the mcopy utility from the ESXi Shell and for accessing an NTFS partition from a USB device in ESXi, you can use ntfscat utility. It actually took me some trial/error to get the correct syntax, but you can see how to use the utilities below.
