I asked this question the other day.
スワップ容量としてUSBメモリを利用したいのですが、USBメモ… - Yahoo!知恵袋
According to the person who answered, at least in the case of Windows, it’s better to use HDD rather than USB as swap capacity. Also, I thought “Won’t that shorten the HDD lifespan?” and asked that too, but everyone does it and it’s fine.
I recently heard about SSD and HDD lifespan, so I might be overly sensitive about that. But well, as long as you don’t make the capacity too large and use it to its full extent, it should be fine.
However, that’s not necessarily the case for Ubuntu.
How to Use Hard Disk As RAM Like In WIndows? - Ask Ubuntu
Using Hard Disk as RAM can be slow. It is recommended to use External fast Devices like flash memory to use as SWAP space.
Translation: Using HDD as RAM is slow. If you’re going to do it, USB memory is recommended.
I was wondering why Linux users abroad use USB even though HDD is faster, and it turns out this is why.