What is SSD? What types of SSDs are there? An article will explain it to you!

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A solid state drive (SSD) is a data storage device that uses flash memory to store data, which has faster read and write speeds, lower power consumption, and higher reliability than traditional hard disk drives (HDDs). SSDs have been widely used in a wide range of computing devices, from personal computers and servers to mobile devices. This topic describes the structure, working principle, types, advantages and disadvantages of SSDs, and application scenarios.

The structure of the SSD

The main components of an SSD include:

1. Flash memory (NAND Flash): This is the core part of the SSD and is used to store data. Depending on the manufacturing process and the arrangement of the memory cells, flash memory can be divided into SLC (single-layer cell), MLC (multi-layer cell), TLC (triple-layer cell), and QLC (four-layer cell). SLC is the fastest and longest-lasting, but it also has the highest cost. QLC has the highest storage density and lowest cost, but poor performance and longevity.
2. Controller: The controller is responsible for managing data reads and writes, performing tasks such as error correction, optimizing performance, and extending flash memory life. It is equivalent to the brain of the SSD, and different brands and models of SSDs usually use different controllers, which is also one of the important factors affecting the performance of the SSD.
3. Cache: In order to improve the data read and write speed, SSDs are usually equipped with a certain amount of cache. The cache can be DRAM (Dynamic Random Access Memory) or it can be part of the flash memory itself. The existence of caches can effectively reduce the latency of data access.
4. 接口（Interface）：SSD通过接口与计算机系统进行数据传输。 常见的接口有SATA（串行ATA）、PCIe（Peripheral Component Interconnect Express）和M.2等。 不同接口的传输速率和性能差异较大。

How SSDs work

The working principle of SSDs is mainly based on the storage mechanism of flash memory. Flash memory is a non-volatile storage medium that holds data even in the event of a power outage. Its basic memory cell is a floating-gate transistor, which represents binary information (0 or 1) by controlling the voltage to store a charge in the floating-gate.

In SSDs, data is read and written through the controller. The read operation is relatively simple, and the controller reads the data from the specified address and transmits it to the host. Writes are much more complex because flash is slower to write and needs to erase data before it can be written.

Erase operations for flash memory are typically performed in "blocks", while write operations are measured in "pages". Since each write requires the corresponding block to be erased first, this makes the write performance of SSDs more complex than HDDs. To solve this problem, the controller uses techniques such as Garbage Collection and Wear Leveling to optimize performance and extend flash life.

• Garbage collection: When there is a part of the data on the SSD that becomes invalid (such as a file being deleted or modified), the controller will periodically perform garbage collection, reorganize the valid data and write it to a new block, and then erase the old block to free up space.
• Wear Equalization: Due to the limited write life of flash memory, the controller uses wear leveling technology to ensure that all blocks are written approximately the same number of times, preventing some blocks from being corrupted prematurely.

The type of SSD

Depending on the interface and purpose, SSDs can be divided into the following types:

1. SATA SSD: SATA is the most common SSD interface and is mainly used in the consumer market. SATA SSDs typically have a transfer rate of 6Gbps, which is a significant improvement in performance compared to HDDs, but slightly inferior to SSDs with other interfaces, such as PCIe SSDs.

1. PCIe SSD: SSDs with PCIe interfaces have higher transfer rates and are commonly used in fields such as high-performance computing and data centers. PCIe SSDs can provide transfer rates of several GBps, which is several times faster than SATA SSDs.
2. M.2 SSD: M.2 is a miniaturized interface standard that is widely used in devices such as ultra-thin laptops, desktops, and servers. The M.2 port can support both SATA and PCIe modes, and the M.2 SSD in PCIe mode is more powerful.

1. NVMe SSD: NVMe (Non-Volatile Memory Express) is an SSD-optimized protocol designed for PCIe interfaces. NVMe SSDs offer better performance than traditional AHCI protocols, with lower latency and faster read and write speeds.

Advantages and disadvantages of SSDs

Merit:

1. Fast speed: SSDs have much higher read and write speeds than HDDs, especially in terms of random read and write performance. This makes things like system booting, program loading, and file transfer much faster.
2. Low power consumption: SSDs have no mechanical parts and consume less power than HDDs, making them ideal for notebooks and mobile devices, helping to extend battery life.
3. High reliability: SSDs have no moving parts, are not susceptible to shocks and shocks, and have a low risk of data loss. In addition, the failure mode of SSDs is relatively predictable, allowing for early warning.
4. Low noise: Since there are no mechanical parts, SSDs operate with little to no noise, making them ideal for applications that require a quiet environment.

Shortcoming:

1. Higher cost: Although the price of SSDs has decreased in recent years, the cost per unit of storage is still high compared to HDDs, especially for high-capacity SSDs.
2. Limited lifespan: Flash memory cells have a limited number of writes, and although modern SSDs extend their life through various technologies, long periods of high-volume write operations can still lead to performance degradation or even corruption.
3. Limited capacity: SSDs on the market today are typically in capacities ranging from a few tens of gigabytes to several terabytes, and while they are able to meet most needs, they are still inferior to HDDs in terms of extremely large capacity storage.

Application scenarios of SSDs

SSDs are widely used in various fields due to their excellent performance and reliability.

1. Personal Computers: SSDs have become an indispensable storage device in personal computers. Whether it's a desktop or laptop, SSDs can dramatically improve system responsiveness and optimize the user experience.
2. Servers and data centers: In the server and data center field, SSDs greatly improve data processing and access efficiency due to their high performance and low latency, especially in applications such as high-frequency trading, database management, and virtualization.
3. Consumer electronics: From smartphones and tablets to gaming consoles and smart home devices, SSDs are widely used in a variety of consumer electronics to provide fast data storage and access.
4. Enterprise-class storage: Enterprise-class SSDs typically offer higher endurance and reliability, making them suitable for large-scale storage and high-performance computing environments, such as scientific research, film and television production, and financial analysis.
5. Embedded systems: In embedded systems, SSDs are widely used in industrial control, medical equipment, automotive electronics and other fields due to their small size, strong shock resistance and high reliability.

A well-known SSD manufacturer

1. SAMSUNG: A world-renowned large multinational conglomerate with a leading position in the field of solid state drives, with strong performance and reliable quality.
2. Western Digital (WD): The world's largest manufacturer of data storage and hard drives, and its SSD products also have a high reputation in the market.
3. KIOXIA: Rebranded from Toshiba Memory Group, Kioxia is a world-renowned provider of storage solutions that is widely recognized for its flash memory products.
4. Kingston: The world's largest independent manufacturer of memory products, offering a wide range of storage products, including SSDs, with lifetime warranties on memory modules and flash memory cards.
5. ZHITAI: A consumer-grade SSD brand under YMTC, YMTC is an IDM integrated circuit company focusing on the integration of 3D NAND flash memory design and manufacturing.
6. Solidigm: A new brand formed by Hynix's acquisition of Intel's NAND SSD business, which offers a wide range of flash technology solutions.
7. ADATA: Its business covers memory, flash drives, flash memory cards, SSDs and portable hard drives.
8. Lexar: A world-renowned flash memory storage brand, its products cover professional image storage, mobile storage, personal system storage and other fields.
9. Gloway: A well-known memory brand under Jiahe Jinwei Group, it is committed to promoting the localization of computer storage products.
10. Crucial: A brand of Micron Group, using Micron's original granules.
11. PLEXTOR: It also has a certain popularity and user base in the SSD market.
12. SanDisk: Acquired by Western Digital, its products and Western Digital's products can be considered the same.
13. Kimtigo: Focusing on the storage field, SSD product sales are mainly in the Chinese mainland market.
14. GALAXY: Founded in 1994 in Hong Kong, China, GALAXY entered the storage field in 2011, and has launched products in graphics cards, SSDs and other fields.
15. Colorful: A domestic DIY hardware manufacturer, covering graphics cards, motherboards, storage and other products, officially launched its first Colorful SSD product in 2015.
16. Lenovo: A well-known hardware manufacturer, its SSD products are mainly integrated into PC products for users.

There are many other manufacturers in the market that also produce SSD products. When choosing an SSD, in addition to considering the manufacturer's brand, you should also pay attention to the product's performance, capacity, price, reliability, and other factors. At the same time, SSDs from different vendors may vary in performance, features, and application scenarios, so you can choose according to your needs and budget.

SSD lifespan

The lifespan of an SSD depends mainly on factors such as the type of flash memory, the amount of writes, the master algorithm, and the environment in which it is used.

Generally speaking, SSDs with TLC flash memory can last 3-5 years or more under normal use. SSDs with MLC flash memory typically last longer.

The number of writes to flash memory is one of the key metrics that affect the lifespan of an SSD. For example, a 256GB TLC SSD flash chip might have a write life of around 150 - 300TBW (Terabytes Written). If you write 20GB of data per day, you can use it for roughly 20 - 40 years. But in practice, few people can achieve such a high write volume.

In addition, good usage habits, such as avoiding continuously writing large amounts of data when the SSD has too little space left, and avoiding frequent writing operations with a large number of small files, can help extend the life of the SSD. At the same time, suitable environmental conditions such as operating temperature and humidity also have a positive impact on the life of the SSD.

summary

A solid state drive (SSD) is a storage device that uses flash memory chips to store data.

SSDs offer several significant advantages over traditional hard disk drives (HDDs). First, it has no mechanical parts, such as spinning disks and moving read/write heads, so data access is faster, which can drastically reduce system boot times, program load times, and file transfer times. Second, SSDs are more resistant to shock and vibration, run quieter, consume less power, and generate less heat. In addition, SSDs are typically smaller, making them easier to install and use in a variety of devices.

In principle, data is stored electronically in a flash memory chip, which is managed and coordinated by a controller for read and write operations.

Due to their excellent performance, SSDs are widely used in modern computer systems, especially in scenarios that require high speed and response, such as high-end laptops, desktop computers, servers, etc.