According to the question as specified, the only correct answer is number 2, sorting by date desc cannot give the required result regardless of null values.

One of my concerns was adding filegroups and files, having now done some more performance tests, for the requirements of my project, I can happily put all the partitions in...

Again, thanks for the input.

The bit in BOL about only retaining partioned views for backwards compatabilty has been taken out, so I suspect that is not an issue.

I decided...

Thanks for the advice. I actually mis-stated the disk, although it appears as 1 physical disk it is actually 5 disks configured as a single raid-5 disk.

On the point about...