Thanks for the comments
Just a bit nervous if I loose the Bluetooth
Drivers for track pad and keyboard etc.
I would like to split the fusion to have the choice were to put my data /kids films and games etc , I suppose I am a bit of a chicken about the splitting
Well, you probably won't do any harm and as long as you take a full backup beforehand with some kind of disk image software, I think you should be ok. But, imho, what you want to do doesn't make a great deal of sense. A fusion drive works by identifying the most popular portions of your hard disk and keeping them on the SSD where the speed of reading and writing is faster. By 'portions', I mean blocks, that's a level of allocation that's lower than a file (files are made of blocks).
So. let's say you want to manage the fusion thing yourself. You split it, keep your operating system and applications on the SSD part because you want them to load quickly. Even then, perhaps your usage of applications varies over time, so perhaps you have to monitor which applications you use and how often so that you can make the best use of the space on the SSD. Also, there may be portions of the operating system you don't use regularly (telnet, ftp, whole bunch of small stuff), perhaps you'd want to move those over to the hard disk - as long as you know what can be moved and what's used. Then, there's libraries - photos, iTunes You can move those over to the hard disk. But, what if there's movies or music you use often and want to come up faster? Can you split iTunes or Photos manually over different disks and even if you could, you'll need to monitor usage again to make sure that your current popular ones are on the SSD.
Oh and importing photos or music. You'll want to have them go to the SSD first because that makes the process faster. So, you'll have to remember that each time.
Meanwhile, the alternative is to have the system as you have it today and everything I've talked about so far gets managed automatically and transparently. Most popular disk blocks kept on the SSD, least popular moved out. 4gb area kept free and new files automatically sent there first and moved to hard disk if they prove to be less popular than other stuff.
Perhaps you have the time and the inclination to manually manage what can be done for you by the system. Personally, I have neither of those things. And even if I did, because I can only see files at my level, I'm sure I couldn't do a better job than the automatic system.
