The Mac Pro has a Flash storage medium which is faster than the HDD storage medium found on most PCs of a similar spec and age to it. Flash Drives 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. Across all computers of a comparable age and type to the Mac Pro the best storage speed is SSD and the worst is HDD.
If the storage speed of this medium processor core personal computer is not fast enough for you then you might also want to consider the Zotac ZBOX CA320 nano (SSD) which also has a higher rating.