BennyFSX

I have the OS on a separate drive (actually the first 120gb partition of a 1terabyte standard drive). This is to ensure there is minimal repeated write activity on the SSD, which will marginally cause performance to deteriorate over time.By having the OS on its own partition on the HDD you can defragment regularly without having to do the same to all your texture files (GEX, REX, etc.), which you can put in a second partition.As for size, I went for 120gb as the certified speed was greater and I wanted to future proof for addon aircraft etc. (The raw FSX install is about 20gb I think, more like 30gb if you have added UTX, GEX, REX.) But 60gb will be fine if you are on a budget - it's a logical place to make savings without a performance hit.