I hope the title wasn't to confusing. I wasn't sure the best way to word this. I bought an i5 15" MBP last week and instantly through my 80GB SSD into it. I've been doing my best to keep a lot of unnecessary data off the SSD but I'm still running out of space. I'm thinking about throwing the stock 5400rpm 320GB drive into an Optibay tray and using that to hold the data. I use Photoshop and Illustrator quite a bit and I would like to use the 5400rpm drive as the scratch disk as well. However, I'm not to familiar with read/write processes and I'm wondering if I will see a speed decrease if I use the 5400rpm drive to house the data while leaving the SSD open for the OS and all applications. Should I expect a noticeable decrease in battery life with both hard drives installed as well?