What is SSD?

An SSD (Solid State Drive) is a storage device that uses semiconductor flash memory (NAND Flash) as its storage medium. Unlike traditional mechanical hard disk drives (HDDs), SSDs store data in semiconductors through pure electronic circuits without any mechanical components. This fundamental difference results in significant variations in performance, power consumption, and reliability compared to HDDs.

While the concept of SSDs has existed for quite some time, they’ve only become mainstream storage devices in the past decade or so. In early 2008, only a handful of companies were developing SSDs; today, hundreds of companies, both large and small, are involved in the industry. Whether in the consumer or enterprise market, SSDs have shaken the foundations of two HDD giants—Western Digital (WD) and Seagate—and are replacing HDDs as the mainstream storage solution.

In today’s SSD-dominated era, anyone working in the storage industry who doesn’t understand SSDs is like calling yourself a tech professional without knowing what Silicon Valley is—it’s simply unthinkable. This article will introduce you to this game-changing technology.

Let’s Start with Boot Times

In the past, computers typically took dozens of seconds or even over a minute to boot. You’d start your computer, go make coffee, come back, and it would still be loading. Today, with an SSD, booting takes mere seconds. You start your computer, begin to stand up to make coffee, and the boot assistant already tells you: “Boot completed in 8 seconds, faster than 99% of users nationwide.” Well, forget about that coffee.

Speed is the most immediate benefit users experience with SSDs. But what enables this incredible speed? Beyond being fast, what other advantages do SSDs have over HDDs? Figure 1-1 shows the boot time comparison for different hard drives. To understand this, we need to explore how SSDs work.

SSD Fundamentals

An SSD is a storage product that uses semiconductors as its primary storage medium, with the same form factor and data transfer interfaces as traditional HDDs. Current mainstream SSDs use a storage medium called flash memory. As semiconductor chip technology advances, future SSDs may adopt faster, more reliable, and more energy-efficient media such as 3D XPoint or MRAM. However, since the industry currently relies primarily on flash memory, this discussion will focus on flash-based technology.

Externally, a 2.5-inch SSD in an aluminum enclosure looks virtually identical to a 2.5-inch HDD. Beyond the traditional 2.5-inch and 3.5-inch form factors, SSDs can come in even smaller packages and sizes, such as M.2 interface SSDs.

Internal Architecture

SSDs are constructed using arrays of solid-state electronic storage chips, with the main components being the controller and storage chips—a remarkably simple internal structure. In detail, SSD hardware consists of several key components:

• Controller (the brain of the SSD)
• Flash memory (NAND chips)
• Cache memory (DRAM – optional; some SSDs may only have SRAM)
• PCB (including power chips, resistors, capacitors, etc.)
• Interface (SATA, SAS, PCIe, etc.)

The SSD’s main body is essentially a PCB (Printed Circuit Board). From a software perspective, SSDs run firmware that manages data read/write operations from the interface to the storage medium. This includes embedded core algorithms for flash memory lifespan and reliability management, along with other internal SSD algorithms. The controller, flash memory, and firmware constitute the three core technologies of an SSD.

Storage Media Types

Storage media can be classified into three main categories based on their physical materials:

1. Optical storage media – DVDs, CDs, and other optical discs that require optical drives for data reading/writing
2. Magnetic storage media – The technology behind HDDs that dominated personal and enterprise storage before SSDs
3. Semiconductor storage media – The foundation of SSDs, breaking HDD’s market monopoly

Semiconductor storage media is experiencing the fastest technological evolution, with multiple emerging technologies including:

• Flash memory (current mainstream)
• 3D XPoint (PCM)
• MRAM
• RRAM

Current Market Landscape

The primary flash memory manufacturers currently include:

• Samsung
• SK Hynix
• Kioxia (formerly Toshiba Memory)
• Western Digital (WD)
• YMTC (Yangtze Memory Technologies)

These companies dominate the flash memory market, though new players may emerge in the future, offering users more choices and driving further innovation in storage technology.