There's been a bit of concern floating around about the relatively small 802GB of available internal storage on the Xbox Series X (and it'll be even less on the Xbox Series S), but Microsoft has been very clear that you don't need to use any of that storage for playing backwards compatible games if you don't want to.
Instead, you can use any old external hard drive or SSD to play original Xbox, Xbox 360 and Xbox One games with added performance benefits, and while the difference in loading times can vary, it might be less dramatic than you think.
Part of the reason for this is because these games don't utilise the full power of the console's "Xbox Velocity Architecture", and the result is that using an off-the-shelf external SSD or a faster NVMe equivalent can produce almost identical load time results to the internal drive / 1TB Expansion Card.
"First of all, I found that loading times could vary a touch from run to run, even on the same drive, but the end result sees that while the internal drive on Xbox Series X is almost always the fastest solid state option, the actual load time advantage up against other SSD solutions is barely noticeable. My results varied from no difference whatsoever to just over two seconds."
You can see detailed examples of this in the video above, which also shows that standard mechanical USB hard drives are much slower than their SSD counterparts as expected, although again load times can vary from game-to-game, so it's not all bad news there if you're planning to use one.
In a nutshell, this means you can still enjoy your old Xbox, Xbox 360 and Xbox One games on your new console without having to clog its valuable internal storage (which you'll require for next-gen and "Optimized for Xbox Series X|S" titles), and you won't necessarily need to break the bank in the process.
Are you planning to use an external drive with your Series X|S? Let us know in the comments.