How much HDD space does BF3 consume?

Minimum System Requirements
OS: WINDOWS VISTA (SERVICE PACK 2) 32-BIT
PROCESSOR: 2 GHZ DUAL CORE (CORE 2 DUO 2.4 GHZ OR ATHLON X2 2.7 GHZ)
MEMORY: 2 GB
HARD DRIVE: 20 GB
GRAPHICS CARD (AMD): DIRECTX 10.1 COMPATIBLE WITH 512 MB RAM (ATI RADEON 3000, 4000, 5000 OR 6000 SERIES, WITH ATI RADEON 3870 OR HIGHER PERFORMANCE)
GRAPHICS CARD (NVIDIA): DIRECTX 10.0 COMPATIBLE WITH 512 MB RAM (NVIDIA GEFORCE 8, 9, 200, 300, 400 OR 500 SERIES WITH NVIDIA GEFORCE 8800 GT OR HIGHER PERFORMANCE)
SOUND CARD: DIRECTX COMPATIBLE
KEYBOARD AND MOUSE
DVD ROM DRIVE

Recommended System Requirements
OS: WINDOWS 7 64-BIT
PROCESSOR: QUAD-CORE CPU
MEMORY: 4 GB
HARD DRIVE: 20 GB
GRAPHICS CARD: DIRECTX 11 COMPATIBLE WITH 1024 MB RAM (NVIDIA GEFORCE GTX 560 OR ATI RADEON 6950)
SOUND CARD: DIRECTX COMPATIBLE
KEYBOARD AND MOUSE
DVD ROM DRIVE

http://www.battlefield.com/battlefield3/1/bf3-faq

does the DVD need to be in the drive in order to play, or does it copy all the contents to the drive

I'm considering getting Premium

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I just realized I need to buy the Battlefield 3 game First, and then get Premium (which is only DLC)
that's about $100 including tax - is it worth it???