- caching in ram
- on disk cache
- an explicit read cache device
All of these are broadly applicable and effective to the other 99.9% of actual devices.
It's neat old Mac's from the 80s could to do that...but they had to be able to do that in order to be useful. In other words, it wasn't a "cool feature", it was something they had to be able to do.
I imagine that when storage became more plentiful OS developers became less interested in implementing solutions to problems of this nature and who can blame them really. Supporting a use-case that almost no one cares about anymore is rather unrewarding.
As others have mentioned, there are plenty of ways to achieve this on Linux today, they just seem to involve more fiddling than you'd like. That, unfortunately, is the nature of the beast.
Linux is a tinkerers OS (that just happened to become popular for servers) and expecting it to change its stripes is asking a lot :-)
You say this like making an application this way is some difficult problem. The whole point of me pointing out that it was the way applications worked on a Mac in 1984 (or indeed any of a dozen other desktop OSs) is that it isn't actually difficult at all. The difficulty it appears to have on Linux is all artificially induced by the culture of Linux software development.
> Linux is a tinkerers OS (that just happened to become popular for servers) and expecting it to change its stripes is asking a lot :-)
I don't expect it to change. I've been hoping Linux people would see the light for 20 years and it hasn't changed. That doesn't mean I have to like it or pretend that it's a good idea.
That isn't the point. I have in my possession several small form factor computers that have 16GB disks in them. "just spend $80-100 each on them" is not a good excuse for having such an inflexible system that it demands everything be on one disk.
The original Mac did this on floppies in 1984. It is 2021, our software should be able to do better.