Switching computers with Raid

So I have a 2 TB raid drive which was solely connected to my Mac Pro Tower doing auto backups until last week when I got rid of the tower to just use my MBP. My question is that because I had about 1.5TB being stored, and now my laptop is only 500GB, what happens when I connect the two?

I want to use the MBP as my station so I would always have it connected to the raid drive so I can access all of my files that were on my tower and now solely on my raid drive, but I don't want to connect and have it do a time machine sync and wipe everything and back up whats on my mbp.

Do I need to lock my raid drive and buy another hd as I still want it to be getting back ups?

I'm just afraid to connect them and lose everything basically.

Thanks!

 

Bump. Any help?