How to mirror Dedicated Server

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http://superuser.com – I bought a dedicated server with cent os from 1&1. I want to upgrade the cent os version on dedicated server. Before that, i want to take a mirror of the server for backup. It hosts many websites. Please let me know how i can do that. I have parallels plesk installed on the server. I only have ssh access to server and it is on 1&1 infrastructure (HowTos)