This issue is largely documented here, it seems that TeXStudio does not automatically adapt its preview tool to the compiler used. This apparently caused a bug which ended up filling up the OP's hard-drive. The issue was not easily reproducible though, so it may be hard to solve.
Expected behavior
Preview command changes with compiler, i.e. compiling with pdflatex imposes a pdflatex preview, lualatex a lualatex preview, etc.
Actual behavior
Preview and compilation commands are independent, which may cause the aforementioned hard drive filling up process.
Environment
This issue is largely documented here, it seems that TeXStudio does not automatically adapt its preview tool to the compiler used. This apparently caused a bug which ended up filling up the OP's hard-drive. The issue was not easily reproducible though, so it may be hard to solve.
Expected behavior
Preview command changes with compiler, i.e. compiling with pdflatex imposes a pdflatex preview, lualatex a lualatex preview, etc.
Actual behavior
Preview and compilation commands are independent, which may cause the aforementioned hard drive filling up process.