Storage vendors have dragged some hefty baggage into the 21st century. The basic IDE interface, for example, is more than 20 years old; SCSI traces its roots back to Shugart Associates' SASI interface, introduced in 1979. Perhaps most onerous is the medium itself: A rotating magnetized disk that can cause major headaches under the best data center conditions. Failure of a single drive—or more catastrophically, an entire array—and it's twilight time for your data.
Fortunately, that's changing.
SSDs, or solid-state drives, sometimes referred to as flash drives, use no moving parts. They consist of large quantities of RAM attached to an appropriate interface. Once packaged, the drives are no different from their spinning platter-based brethren as far as interface controllers on host systems or, for example, large NAS arrays, are concerned. The key difference is the lack of moving parts. Instead of a motor and series of heads, controllers manage data flow from each bank of RAM, passing information to the attached drive controller, which in turn passes it to the host system. Data access is near instantaneous.