How can two external USB hard drives be connected to two laptops at the same time?

Question

How can two external USB hard drives be connected to two laptops at the same time?

Answer 1

This question touches many aspects, even if it seems simple:

• A hard disk (or a partition on it) is worthless to store files: The filesystem on it is the important part.
• Most file systems (this includes NTFS and [ex]FAT) are built with the assumption, that they only ever will be accessed by one computer at a time
• Most busses used to attach storage are hierarchical in the sense, that one (and only one) participant is the boss, this includes USB (but not SAS).

So attaching USB hard disks to two hosts at the same time is a tricky proposition: Neither the bus, nor most of the file systems are designed to do that.

The typical and most likely best way to tackle this problem is to attach one disk to each computer, then use network shares to make it accessable to the other.