The terms flash storage and SSD (solid state disk) storage are often used interchangeably to describe a type of storage that has no moving parts and can be erased and reprogrammed. Though closely related, they're not exactly the same thing.
What is Flash Storage?
Flash technology dates back to the 1980s when it was invented by Dr. Fujio Masuoka from Toshiba. One of his colleagues is reported to have suggested the name "flash" because the process of erasing the contents reminded him of a camera's flash. Though there are no moving parts to wear out, flash memory has a limited amount of program-erase cycles (P/E cycles) before the integrity of the storage deteriorates.
What is SSD Storage?
SSD arrived long before flash was invented. Early forms of solid state disks, which were referred to as auxiliary memory units, were used in the 1950s but fell out of favor when less expensive drum storage units emerged. In the 1970s, SSDs were occasionally incorporated into the semiconductors that powered supercomputers, but they were cost prohibitive. The 1980s saw the introduction of solid state storage cartridges and memory modules. However, some issues such as the loss of content when the storage chip was not powered meant that usage was limited unless a backup battery was provided.
When flash technology emerged, the flash-based SSD soon followed in the mid-1990s. This solved the power requirements related to maintaining the contents of the memory.
Today, flash and SSD technologies are everywhere. Tiny cards inside your digital camera allow you to save hundreds of high resolution photos and videos; USB drives allow you to store many gigabytes of data on a tiny stick and then take it with you; modern ultrabooks come with SSD instead of bulky hard disks, making these devices thin and light.
In addition to being able to pack a lot of capacity onto a tiny chip, flash and solid state storage devices are fast. Startup is nearly instantaneous; they deliver consisted read and write speeds; they don't require special cooling and can handle higher temperatures than hard disks; because there are no moving parts, they are also resistant to shocks and vibrations; there are no moving parts to fail; and their power consumption is about half as much as a hard disk drive.
However, like early forms of SSD storage, costs remain high. When compared to hard disk drives on a per gigabyte basis, the cost differences are astounding. Though costs have dropped, the gap between SSD and hard disk drive prices remains expansive.
What is Hybrid Storage?
One solution that bridges that gap is hybrid storage. Hybrid storage uses a combination of flash storage and traditional hard disk drives to create a storage solution with the performance and reliability of SSD and the capacity and cost advantages of hard disk drives. The concept here is that data used most often resides on the faster, high performance flash drives while data that just needs to be stored until needed resides on traditional hard disks.
In the battle between flash storage vs. SSD vs. hard disks, the clear winner is a blend: hybrid storage.