The Apple Mac Pro Late 2013 has an SSD storage medium which is faster than the HDD storage medium found on most similar spec desktop computers that have been around for a comparable time to it. Solid State Drives (SSD) store information in transistors on a circuit board rather than on optical or magnetic media. This has the advantage of being much faster than a traditional HDD drive.
An SSD storage medium is in fact the best storage speed across all medium processor core computers that have been around for more than a year.
An HDD storage medium is the worst storage speed amongst similar types of personal computer.