The Lenovo Flex has an HDD storage medium which is better than the SSD storage medium found on most notebook PCs of a comparable spec and age to it. HDD is a traditional storage drive which stores the information on magnetic disks. HDD drives are slower than other forms of storage such as solid state drives (SSD) and flash drives.
This notebook PC's storage medium (HDD) is actually the worst storage medium across all 2 in 1 laptops that have been available for a similar time to the Flex.
The best storage medium amongst comparable types of notebook PC is SSD.