Yes Gazwas, we got a little sidetracked. apologies.I appreciate all your replies but I feel your getting a little obsessed by speed. My main wish is data safety over speed and as kindly explained by narikin RAID 5 or 6 seems like the best deal to me.
Sorry for the very basic question but never even considered NAS before today, (thought it was for xbox/TV etc) If I opt for a NAS system why do they come with their own memory and processor and what effect does the processor speed have on the unit?
NAS are completely self contained little computers, with processors, power supplies, etc. and as they don't really do anything but control a bunch of disks, and connect with the Ethernet, they are very happy with low power processors. I have never had one break, or noticed it as being 'slow'.
You don't sound uber-technical (and nor am I despite my modest Raid experience) so just be sure you are happy setting up a NAS. It's really not that complicated, unless you want to do something more fancy, like setting up your NAS to be accessible from outside the home (eg for a traveling photographer who needs to see files sometimes from far away). I have mine set up for that, and to act as time machine backup for girlfriends Powerbook. works perfectly. I am extremely happy with my Qnap.
If its just internal home network use, and RAID protection of your data, then its kind of perfect. Raid 5 is the de-facto standard for most people. Raid 6 is for the paranoid.
Good luck.