Hard drive and audio I/F configuration

[Xenon20]

Hi all

I have 3 drives which are all 1TB each.
1. 1TB SSD inside iMac (recently replaced a 1TB Seagate HDD)
2. 1TB My Book (FW800/USB2)
3. 1TB WD (USB2)

Before I installed the SSD, I used the Seagate HDD for my OS and programs and my sample library, the WD (USB2) for time machine backups and the My Book to store my music projects. The my book (projects) drive was connected to the mac using FW800 and my audio I/F was chained off of this drive using FW400.

I am a new Ableton user and am looking to make sure I organise my files properly as well as choosing the right drive configuration for optimum performance.

Now that I have the SSD installed, Is there a need to use seperate drives for OS & Programs / Sample Libraries and Projects ? My Mac is only used for music production but as time goes on I expect that the 1TB SSD will become full.

How would you go about setting up these drives in my situation ?

Thanks

Paul