The ZBook 17 has a better storage medium than most many processor core portable PCs that were launched around the same time as it. This portable PC has an SSD storage medium, whereas most notebook PCs of a comparable type and age 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.
This notebook PC's storage medium (SSD) is in fact the best storage medium amongst all similar spec laptops that have been available for a comparable time to the ZBook 17.
The worst storage medium amongst comparable types of notebook PC is HDD.