The Acer Chromebox CXI has a faster storage speed than most few processor core personal computers that are a similar age to it. This desktop computer has an SSD storage medium, whereas most personal computers that were released around the same time as it have an HDD storage medium. 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 personal computers of a comparable age and spec to the Chromebox CXI.
The worst storage speed across comparable types of computer is HDD.