The HP Z420 has an HDD storage media which is faster than most many processor cores desktop computers that have been on the market for a comparable time to it. Most personal computers of this spec and age have a Flash storage media. A Hard Disk Drive (HDD) is the traditional storage method for computers. A HDD stores the information on magnetic disks. HDD drives are cheap, but they are slower than Flash and SSD bases storage systems.
This computer's storage speed (HDD) is actually the worst storage speed amongst all many processor cores desktop computers that were launched more than two years ago.
The best storage speed amongst comparable types of computer is SSD.