I've recently installed a Crucial m4 512GB into a 2011 MBPro running 10.6.8 I have cloned my old hard-disk. But: how large a partition should one format the new Crucial SSD? From various reading, I assumed that OSX would show the 512GB SSD as approx 480GB of useable space (due to 7% being left "spare" for the Crucial SSD firmware/defrag/garbage collection etc). However, OSX currently lists the drive as being a single 511.2GB partition. Please note that I have also installed the TRIM hack. Today I noticed that on my 2011 mac mini with Apple installed 256GB SSD, OSX displays the size as 251GB - i.e. smaller than 256GB, but proportionally much larger than is expected for a SSD with a spare area of 7% (expect approx 240GB). Is there in fact any reason/need to format the new 512GB drive to 480GB (or smaller)? What size (useable) do others see OSX reporting for SSDs (both installed by Apple and user installed)?