cpu and exrenal hard drive question

[Reasonable man]

Hi.
I'm not planing to run Reason off an external hardrive (unless people think that its a good idea) just for saving different versions of tracks as i go. Currently i just use my laptop for everything .
A video i watched recommends using an external ssd drive and saving your projects on that as you go along as it is a massive cpu saver. I dont have an external drive currently but im going to . The thing that confuses me (cause it wasn't explained in the video) is that mosly i presume this just saves space on your computers c drive as reason is running but would it really help cpu performance?
If your using your computer's internal drive to save song files surley this dosn't tax actual performance too much (especially if you have alot of space) .
I understand having a seperate external drive to store everything in case of internal drive failure but i dont understand how the boost in performance is achieved . I have a budget set up (to say the least!) but i'm trying to get as effecient with it as possible and working out what is the best way of doing this. Can someone who uses this method explain the benifit of getting and using an external ssd drive to help with cpu? Thanks.

[demt]

something to do with loading large audio files

[QVprod]

It's more so a benefit with audio recording and mixing (with audio files). The idea is to put less strain on the system drive so the drive isn't reading and writing simultaneously, which is beneficial for performance and the health of the hard drive.

[Reasonable man]

cheers