The HP ZBook 15 has a better storage medium than most laptops that have been around for around the same time as it. This notebook PC has an SSD storage medium, whereas most notebook PCs that have been available for a comparable time to it have an HDD storage medium. 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 medium is in fact the best storage medium across all many processor core portable PCs that came out around the same time as the ZBook 15.
Across similar types of laptop the worst storage medium is HDD.
Alternative laptops that have an SSD storage media currently available which you might also want to look at include the Lenovo ThinkPad T540[plb_2471953_price], or the HP EliteBook 745[plb_2446437_price] which is cheaper.
If you would prefer a laptop with a better storage medium then you might also want to look at the ZBook 17[pl_2036831_price] (SSD), or the ZBook 15[pl_2156059_price] (SSD) both from HP.