Split install across SSD and HDD - optimum layout?

[Ralf Mardorf]

FWIW among others /var contains cache/apt/archives/.

IMO you should consider to keep the complete root directory inclusive of
/home on the SSD. tmp/ could be either on the SSD or tmpfs.

Data you need for a current project and daily work should be on the
SSD, too, just less often required data should be on the HDD.

However, there are no universal facts what to chose, it likely depends
on the kind of usage.

swap probably could be on the HDD :p.