Flash vs. SSD Storage: Is there a Difference?

Many people use the terms “flash” and “SSD” interchangeably when discussing solid state drives (SSDs)—even experts. While the two technologies are very closely related, the terms don’t refer to exactly the same thing. Most SSDs use flash technology, but not all flash storage drives are SSDs. This guide covers both technologies and the ways they work together.

Flash storage vs. SSD

• What is flash storage?
• What is SSD storage?
• Difference between flash and SSD storage
• The future of flash and SSD
• Bottom line: Flash storage vs. SSD: What’s the difference?

What is flash storage?

Flash is a silicon chip-based storage medium that can be written to and erased with electricity. Flash has characteristics that distinguish it from other storage media, including the following:

• Speed. As the name suggests, it’s fast, much more so than hard disk drives (HDDs).
• No moving parts. Unlike spinning disks or tape, flash can be used to make drives with no moving parts. In general, that makes it less likely to break or fail—particularly in situations where storage is being moved around, like mobile devices.
• Non-volatile memory. Flash retains the information that it stores even when the power is off. That sets it apart from random access memory (RAM), which is very fast but gets erased every time the system powers down.
• Rewriteability. Flash is easily rewriteable, so it’s useful for storing data that changes frequently (unlike, for instance, a CD or DVD).

Flash can be used for many devices in addition to SSDs. Examples include phones, laptops, digital cameras and video cameras, memory cards, USB memory sticks and medical devices. Even some digital toys use flash storage.

Flash comes in several different varieties. The two most common are NOR and NAND:

• NOR was the first of the two to be developed. It is very fast for reads, but not as fast for writes, and is most often used in places where code will be written once and read a lot. 
• NAND is faster for writes and takes up significantly less space than NOR, which also makes it less expensive. Most flash used in commercial and enterprise SSDs is NAND.

The biggest downside to flash is that, until the last decade or so, it was fairly expensive. However, as flash technology has improved and been more widely distributed, the cost has decreased, making flash more cost effective for enterprise environments. Some organizations are even choosing to do away with HDDs entirely and convert to all-flash SSDs in their data centers.

If you’re in the market for an all-flash array, see our list of the best all-flash storage vendors.

What is SSD storage?

A solid state drive, or SSD, is a storage device. Any type of storage that isn’t in motion counts as an SSD. Some solid state drives use the same form factors as HDDs. This makes it easier for users to migrate from disk-based storage to solid state storage. Enterprises can purchase individual drives or SSD arrays already populated with drives. Hybrid arrays, which use a combination of HDDs and SSDs, are another popular option.

Other solid state drives use newer form factors, like M.2 and EDSFF. The M.2 form factor is a narrow and slender drive that fits easily into computer motherboards. Samsung, along with other vendors like Kioxia, Crucial and Western Digital, has popularized this form factor. EDSFF, the Enterprise and Data Center Standard Form Factor, is a recent development designed to handle more demanding workloads than standard M.2 and 2.5-inch form factors can.

In the market for the best SSDs? See our list of the best and fastest SSDs.

Difference between flash and SSD storage

While flash and SSDs are often compared, they measure two different things. Flash is a technology by which data is stored while SSDs are a storage device. 

Not all SSDs use flash as their storage medium, but most currently on the market do. For those, the relationship between flash and SSDs is similar to the relationship between a CD and a CD drive. The CD is the medium and the CD drive is the storage device, just like flash is the medium and the SSD is the storage device. 

The oldest solid state drives relied on a type of computer chip called EAROM, or electrically erasable read only memory. Later manufacturers sold SSDs based on RAM. Like flash, RAM is fast, but unlike flash it is volatile, which means that everything stored in RAM is erased when the power is turned off. This poses huge problems in the case of a power outage, so many of these early SSDs had battery backup systems.

Early flash was expensive. That price tag put flash out of reach for most applications, and it also wasn’t as fast as RAM. However, the non-volatile nature of flash made it appealing enough that researchers continued developing it even as they sold RAM SSDs. Gradually, increased popularity and availability took the price down. 

While flash-based SSDs are now the most common type of solid state drive, they aren’t the only ones to exist. 

The future of flash and SSD

While flash-based SSDs are still more expensive than hard drives overall, their price has stabilized, and they’re no longer a novelty. However, using flash for an entire storage environment—rather than a combination of flash-based storage for critical applications and disks for archiving—is still rare. Flash is still not affordable enough for the majority of businesses to use for all their storage. This may change in the next few years as vendors like Pure Storage popularize all-flash storage arrays. 

Bottom line: Flash storage vs. SSD: What’s the difference?

For the foreseeable future, most SSDs will continue to be based on flash storage technology. And that likely means that much of the storage industry will continue using the terms “flash” and “SSD” interchangeably. But it’s good for experts and personnel to know the difference while analyzing storage technologies.

Read more about the flash storage market next.