The Asus UX31A has an SSD storage media which is better than most portable PCs of this type and age. Most notebook PCs that were released more than two years ago have an HDD storage media. Solid State Drives (SSD) store data in semiconductors on a circuit board rather than using magnetic or optical media. Solid State Drives have no moving parts which makes them very fast and reliable.
This laptop's storage medium (SSD) is actually the best storage medium across all medium processor cores notebook PCs that were launched more than two years ago.
The worst storage medium across comparable types of laptop is HDD.