Why use Redis instead of storage in normal variables?

What is the advantage of using Redis for session storage over simply storing all data in variables inside your app?

From the top of my head:

Pros of storing sessions in external storage (redis) vs in-process

  • sessions survive crash of app server
  • sessions are shared between all app servers (if you have more than one).

Cons:

  • slower than storing in-process (because of network latency)
  • requires setting up and managing the storage