Oh oh, Neil, I didn't realize that...about how the SSD fills up (with operating system and programs), spills over to the HDD, and then the HDD slows down the system.
I see now what you mean about ideally a computer should have just one big SSD and no HDD, for top speed.
Cost wise that wasn't possible when I set up this Asus. It came with the 2 T HDD. And I did want that kind of storage space on the computer - so speed wasn't my first or highest concern. I certainly needed the RAM upgrade more than I needed addtional speed, so I bought a little bit of both.
About speed, though, I'm still not clear about the situation with the 2 drives - if a computer keeps only storage items on its HDD (photo, docs etc), does that slow down the speed of the SSD?
On this Asus, clearly I'm in little danger of filling up the 512 GB SSD with OS and programs since, after 5 years, I'm still only using 80 GB of SSD. But let's say, max, I use up 200 GB of SSD, so still about half empty SSD. Then, continuing to use the HDD for only storage, how much of the HDD can I fill up before that will affect performance? Also half of it, i.e. 1T ? - which is what I would like to do. Or is that not how these things work ? lol.
Of course, your explanation now makes me wonder about my much more expensive iMac. It also has 2T HDD but only 128 SSD! Though I realize that Apple uses some sort of magic proprietary system to optimize the two drives as a Fusion Drive, whatever that might mean. (btw, just to mention that they intended to replace both drives on my broken Mac, but when I go it back, they had only replaced the SSD. It seems to be working well, though I don't have much on it yet.)
Looking forward to your reply, as usual :)
Skye