In a wheelset for Road Bike, mainly for rear wheel, the 2:1 Spoke Pattern has less spokes but better stiffness than the Regular Spoke Pattern, the concept is to put more spokes on the Drive Side and less on the None-Drive Side.
Increased lateral stiffness: The traditional regular spoke pattern has 12 spokes for the Drive Side of a road bike, but 2:1 pattern has 14 spokes for Drive Side. 2 more spokes in 3 Cross lacing increase the Lateral Stiffness for the road bike wheel. The 2 more spokes in the Drive Side also bring other benefits as the following,
Transfering the driving torsion better: due to the increased lateral stiffness, your driving power transmitted to the wheel more instantly.
Less stress for the rear wheel spokes: the stress spreads to more spokes, so each single spoke burden less stress than the regular pattern wheel, this also extends the spokes’ life.
Lighter weight: There are 24 spokes in a traditional spoke pattern wheel, while there are 21 in a 2:1 pattern one. 2:1 pattern saves 3 spokes and nipples for your road bike.