The ZBOX CA320 nano has an SSD storage medium which is faster than the HDD storage medium found on most PCs that have been available for around the same time as 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 actually the best storage speed across all computers that are a comparable age to the ZBOX CA320 nano.
Across comparable types of PC the worst storage speed is HDD.
It may also be worth also looking at one of the other SSD desktop computers currently available including because of it's better review score, the DELL Precision T1700 SFF ($749.99).