In recent years, solid-state drives (SSDs) have taken the computer industry by storm. The technology has impressive capabilities. It promises low-latency access to sometimes critical data while increasing overall performance—at least when compared to what is now becoming the legacy hard disk drive (HDD). With each passing year, SSD market shares continue to climb, and in many sectors, SSDs have been replacing HDDs (for example, personal and mobile computing).
The HDD was first unleashed into the computing world by IBM in 1956. By the 1960s, the HDD became the dominant secondary storage device for general-purpose computers. The primary characteristics that define the HDD are its capacity and performance. The first IBM-manufactured hard drive, the 350 RAMAC, was as large as two medium-sized refrigerators with a total capacity of 3.75MB on a stack
of 50 disks. Modern HDD technology has produced disk drives with volumes as high as 12TB, specifically with the more recent Shingled Magnetic Recording (SMR) technology coupled with helium. The sealed helium gas increases potential speed of the drive while creating less drag and turbulence. Being less dense than air, it also allows more platters to be stacked in the same space used by 2.5” and 3.5” conventional disk drives.
The performance of a disk drive is typically specified by the time required to move the drive’s heads to a specific track or cylinder and the time it takes for the requested sector to move under the head—that is, the latency. Performance is also measured by the speed that the data is transmitted. Now, although the performance of HDDs has been increasing with newer protocols (Parallel ATA or PATA, Serial ATA or SATA, and even Serial Attached SCSI or SAS) and technologies, it is still a bottleneck to the CPU and, in turn, the overall computer system.
Since its conception, engineers have been devising newer ￼and creative methods to help accelerate the performance of HDDs, completely replacing them in some cases.