best practices: when to use parameter server and when not?

Hi, I was wondering what experiences people have had from using the parameter server... 1. What cases must you use the parameter server? What types of data would you not read through the parameter server? 2. What cases should you use some other methods, like a shared memory file? 3. When should you use command line arguments? 4. What other options do you have in addition to these? Thank you