i have 2x 2tb hard drives - one is at work, and the other stored at home - pictures are mirrored on both of them
i figure if something wipes out boths drives, then i have bigger issues than missing pictures.
on the drives stuff is sorted by category
i have the following categories
Motorsport (further split into Drift, Circuit, Dirt Rally, Tarmac Rally, Bikes)
Work (basically anything i have shot at work)
each set of pictures (each job or event) is in its own folder and dated named with YYYY MM DD (my initials) (3 letter code for job type, GEN for general, SPT for sport etc) followed by a description of the job
for example - Darling 200 Rally last year is labelled "20121117 BZC MOT Darling200 Rally SS 1 3 5"
that breaks down to 17th Nov 2012, Motorsport, Darling 200 Rally, stages #1, #3 and #5