The HP ProBook 655 G1 has an SSD storage media which is better than the HDD storage media found on most many processor cores laptops that were launched more than two years ago. 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.
An SSD storage media is in fact the best storage medium amongst all portable PCs that were launched around the same time as the ProBook 655 G1.
Amongst similar types of portable PC the worst storage medium is HDD.