Understanding SSDs: Everything You Need to Know


What is an SSD?

An SSD (Solid State Drive) is a storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory. Unlike traditional Hard Disk Drives (HDDs), SSDs have no moving parts, making them faster, more durable, and quieter. The term “solid state” distinguishes it from earlier storage technologies that used vacuum tubes and mechanical parts.

Why is it Called a “Solid State” Drive?

The name “solid state” reflects the fact that SSDs are built entirely from solid components. Early computers used vacuum tubes where electrons moved through a vacuum rather than solid material. Modern SSDs use silicon-based transistors where electrons move through solid-state circuits, hence the name.

Key Differences Between SSDs and HDDs

  • No Moving Parts: SSDs operate silently and are more resistant to physical shock.
  • Energy Efficient: SSDs use less power compared to HDDs, which rely on spinning disks and moving read/write heads.
  • Faster Performance: SSDs can access and transfer data much more quickly than HDDs.

SSD vs HDD: How to Choose?

Both SSDs and HDDs have their advantages, and the best choice depends on your needs and budget. Here are some key points to consider:


SSDs are much faster than HDDs because they use flash memory to store data instead of mechanical parts. This means SSDs can boot up your operating system, load applications, and transfer files much quicker. For instance, PCIe Gen 5 NVMe SSDs can reach speeds over 10,000MB/s, while HDDs are limited by their mechanical design and can’t surpass these speeds. If you need fast performance for gaming, video editing, or other intensive tasks, an SSD is the better choice.


SSDs are generally more expensive than HDDs, but their prices have decreased significantly over the years. SSDs are now affordable for most consumers, although HDDs still offer more storage for the price. When comparing cost per unit of storage, HDDs remain more cost-effective, but SSDs provide better performance for the investment.


HDDs typically offer larger capacities at lower prices. If you need a lot of storage space for backups or archives, HDDs might be more suitable. While SSDs are commonly available in capacities ranging from 120GB to 4TB for consumer models, HDDs can reach up to 24TB and beyond. However, in the consumer market, SSDs usually range from 4TB to 8TB, with enterprise solutions offering capacities above 100TB, though they are not easily accessible for average users.

Durability and Reliability

SSDs are generally more durable than HDDs because they lack moving parts. HDDs can suffer physical damage from shocks and vibrations, leading to data loss. SSDs, on the other hand, do not have mechanical components, reducing the risk of mechanical failure and high-frequency noise during operation. However, SSDs are not immune to failure; they have a limited number of write cycles. Additionally, recovering data from a failed SSD is often more challenging than from an HDD.

Best Practice: Use Both

For optimal performance and storage, consider using both SSDs and HDDs. Install your operating system and frequently used applications on an SSD for speed, and use an HDD for large files and backups.

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Regarding internal SSDs, although they offer slightly better performance, it’s crucial to pay attention to the slot specifications and their limitations. For example, SATA and PCIe are entirely incompatible. Even within the PCIe interface, differences between generations such as Gen4 and Gen5 can result in varying speeds. Therefore, it’s essential to match your system configuration with the appropriate SSD product. Overall, if you need a fast, secure, and high-performance storage solution, an internal SSD is the better choice. However, if you require portability, storage expansion, or the ability to share data between different devices, an external SSD might be more suitable for your needs.


Internal vs External SSDs

Just like HDDs, SSDs come in both internal and external formats, catering to different usage scenarios.

  • External SSDs: These are great for expanding storage and transferring large files between devices. They connect via USB, Thunderbolt, or other external interfaces. However, the transfer speed will depend on the interface used. For example, an SSD that supports USB 3.2 Gen 2×2 will be bottlenecked if connected to a USB 2.0 port.
  • Internal SSDs: These are typically faster than external SSDs and are installed directly into your computer. When choosing an internal SSD, ensure compatibility with your system’s slots and interfaces (SATA vs. PCIe).

What are SATA and mSATA?

SATA (Serial ATA) is one of the most familiar interfaces for many people, developed from the older IDE/PATA interface, and has been used in computer systems to connect hard drives, optical drives, and other devices. The commonly used SATA 6Gb/s specification (also known as SATA III) has been around for 15 years since its release in 2009. Early SSDs adopted this interface, and although there are higher-speed interfaces like SATA Express and U.2, consumer products supporting them are still scarce.

mSATA, a derivative of SATA, is designed for embedded applications, reducing installation size and commonly found in laptops. Despite this, mSATA offers no significant speed upgrade, remaining at 6Gb/s. While this bandwidth is sufficient for traditional mechanical hard drives, it becomes a limitation for high-speed SSDs, inherently capping at around 600MB/s. As a result, mSATA SSDs are gradually becoming obsolete, except in older laptops.

In modern desktops and laptops, mSATA slots are rarely seen unless there is a need for wireless network card expansion.

在新一代的電腦主機與筆電當中,除非是有無線網卡擴充的需求,否則基本已經看不到 mSATA 的身影。


The Transition from PCIe to M.2

Given that SATA bandwidth cannot meet the demands of SSDs, alternatives like PCIe and M.2 have been developed. PCIe (Peripheral Component Interconnect Express) evolved from the AGP interface initially designed for graphics cards. The latest version is PCIe 5.0, although PCIe 4.0 is still mainstream. Bandwidth varies with the number of lanes (e.g., x1, x4, x8, x16), with a single PCIe 4.0 lane providing close to 2000MB/s, much faster than SATA. Manufacturers transitioned SSDs to use the PCIe interface for efficiency, but PCIe SSDs face size constraints, especially in laptops with limited space for additional interface cards.

Intel championed the new M.2 interface, combining the benefits of various interfaces while being a complex hybrid interface. M.2, initially known as NGFF (Next Generation Form Factor), was promoted by Intel to replace mSATA and first adopted in laptops to encourage miniaturization. M.2 supports multiple signal protocols, including SATA, PCIe, USB, and audio, providing higher flexibility for product design.

主機板上的 M.2 介面插槽。


M.2 Slots on Motherboards

Understanding M.2 Slot Variants

The high flexibility and hybrid nature of M.2 make it complex. There are three main types of M.2 slots: Socket 1, Socket 2, and Socket 3, each with different keying to prevent incompatible insertions. Socket 1 is primarily for wireless network cards and uses A Key, while Socket 2 and Socket 3 cater to M.2 SSDs. Socket 2 supports SATA and PCIe x2 lanes with B Key, whereas Socket 3 supports PCIe x4 lanes with M Key. Some M.2 SSDs are designed with B+M Key to be compatible with both slots.

主機板上的 M.2 介面插槽。


Important Considerations for M.2 SSD Compatibility

Even if an M.2 SSD fits the slot, it might not function if the motherboard only supports specific protocols. For instance, some M.2 slots might only support PCIe lanes, making SATA M.2 SSDs undetectable unless the motherboard includes both SATA and PCIe controllers. Always check your motherboard’s specifications for compatibility. SATA M.2 SSDs also face the 6Gb/s bandwidth limit, performing similarly to 2.5-inch SATA SSDs.

M.2 SSD Sizes

You might see numbers like 2242, 2260, 2280, etc., which denote the size of the M.2 SSD. For example, 2280 means the SSD is 22mm wide and 80mm long. Depending on the memory chip arrangement, there can be single-sided or double-sided configurations. Most manufacturers provide sufficient installation space, but it’s always good to verify.

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Interfaces, Protocols, and Types of Flash Memory


SATA is the most common interface for SSDs, providing good performance and compatibility with many systems. mSATA is a smaller form factor designed for laptops and compact devices but offers similar performance to SATA.

PCIe and M.2

For higher performance, PCIe SSDs are preferred. They connect through the PCIe interface, offering much higher data transfer rates. M.2 is a form factor that can support both SATA and PCIe interfaces, allowing for versatility and high performance.


AHCI (Advanced Host Controller Interface) was designed for traditional HDDs and is used by SATA SSDs. NVMe (Non-Volatile Memory Express) is optimized for SSDs using the PCIe interface, providing lower latency and higher IOPS (Input/Output Operations Per Second).

同樣是 PCIe SSD,支援 NVMe 標準的 SSD 的傳輸效能,硬是比 AHCI 標準高出一大截。


Types of NAND Flash Memory

  • SLC (Single Level Cell): Stores one bit per cell, offering the highest performance and durability but at a higher cost.
  • MLC (Multi Level Cell): Stores two bits per cell, providing a balance between cost, performance, and durability.
  • TLC (Triple Level Cell): Stores three bits per cell, offering higher storage density at a lower cost but with reduced performance and endurance.
  • QLC (Quad Level Cell): Stores four bits per cell, allowing for even higher storage capacities but at the expense of performance and durability.




Maintaining and Optimizing Your SSD

After gaining a deeper understanding of SSD technology, there are several crucial factors to consider when purchasing an SSD to ensure you select the best option for your needs:

  1. Interface and Performance Before purchasing an SSD, you must first understand which interfaces your system supports to buy the appropriate model. If not, you might face compatibility issues, ranging from suboptimal speeds to being unable to install the SSD at all. SSD performance is typically measured by read and write speeds, random read/write IOPS (Input/Output Operations Per Second), and latency. Manufacturers often provide these specifications on the packaging, based on optimal testing conditions. To choose a high-performing SSD, you can also check reviews and test reports to ensure it meets your requirements.
  2. Capacity and Size Next, determine the capacity you need. NVMe SSDs generally range from 256GB to 4TB. Besides considering your application needs and budget, note that buying two 2TB SSDs is often cheaper than a single 4TB SSD. Regarding size, most desktops and laptops support the widely-used M.2 2280 size SSD. However, if you are purchasing an SSD for a gaming handheld or console, check the supported form factor for that device. For example, Steam Deck and ROG Ally support only M.2 2230, while the PS5 supports various sizes, including 2230, 2242, 2260, 2280, and 22110, with performance requirements of PCIe 4.0 x4 or higher. Xbox Series X/S does not support internal SSDs and requires a special SSD expansion card.【2024】SSD 固態硬碟採購:一次搞懂關鍵規格及介面、選容量也要夠耐用,15大SSD選購推薦

  3. Durability Durability refers to the total amount of data that can be written to the SSD, usually measured in TBW (Terabytes Written). A higher TBW means the SSD can handle more write operations, indicating a longer lifespan. Since TBW values often reach thousands of terabytes, manufacturers may also provide DWPD (Drive Writes Per Day) values for easier understanding. DWPD indicates the number of times the SSD can be fully written per day within its warranty period. For example, if an SSD has a DWPD of 0.5 and a capacity of 1TB, it means the user can write up to 500GB of data daily.
  4. Brand and Reputation There are many well-known SSD brands, including Samsung, Western Digital, Seagate, Kingston, Micron, and KIOXIA, among others. These brands generally offer good quality and reliability, with well-established warranty and support mechanisms. While mass production can sometimes lead to occasional defects, purchasing through official channels should ensure good service and resolution. Additionally, beware of counterfeit SSDs on the market. If buying from second-hand sources, ensure the product’s authenticity, especially if the price is significantly lower than the market rate.

11 FAQ about SSDs

Q1: What are some SSD Benchmark Tools?

If you want to test whether your newly purchased SSD performs as the manufacturer claims or check its status and health over time, several well-established SSD benchmarking tools are available online. Here are some common tools, though as an average consumer, you don’t need to run every test in every mode. Just ensure the SSD works properly, as testing each write operation slightly wears out the SSD.

  1. AS SSD Benchmark AS SSD Benchmark tests the read and write performance of an SSD and performs a 4K alignment check, displaying results as scores.【2024】SSD 固態硬碟採購:一次搞懂關鍵規格及介面、選容量也要夠耐用,15大SSD選購推薦
  2. CrystalDiskMark One of the most popular SSD benchmarking tools, CrystalDiskMark has a simple and easy-to-use interface. It tests the sequential and random read/write speeds of SSDs and displays results in MB/s or IOPS.【2024】SSD 固態硬碟採購:一次搞懂關鍵規格及介面、選容量也要夠耐用,15大SSD選購推薦
  3. ATTO Disk Benchmark This tool tests read/write speeds for files ranging from 512B to 64MB, displaying results as bar graphs. It allows customization of queue depth to show SSD performance with small files more intuitively.【2024】SSD 固態硬碟採購:一次搞懂關鍵規格及介面、選容量也要夠耐用,15大SSD選購推薦
  4. PCMark A well-known computer performance testing tool, PCMark included tests for new SSD storage characteristics in 2019, converting results into scores for easier comparison.【2024】SSD 固態硬碟採購:一次搞懂關鍵規格及介面、選容量也要夠耐用,15大SSD選購推薦

Besides these tools, many storage manufacturers offer their own SSD optimization and management tools, such as Samsung’s Magician SSD management tool and Micron’s Crucial Storage Executive application, to optimize SSD performance and extend lifespan.

Q2: SATA SSD vs. PCIe SSD – Which One is Right for You?

If you have a 5-10 year-old computer or laptop that has never had an SSD installed, even if it has an M.2 slot, you might not be sure if it supports the PCIe NVMe protocol. In this case, replacing the HDD with a SATA SSD is the safest choice. Although SATA speeds are slower than PCIe, SSDs still offer a significant performance boost compared to traditional HDDs, roughly 3-5 times faster.

For newer computers or laptops (within the last 2-3 years), first confirm the supported PCIe interface specification – PCIe 3.0, 4.0, or 5.0 – and the number of lanes used. This will ensure you fully utilize the speed advantages of a PCIe NVMe SSD, enhancing gaming experiences or work productivity.

Q3: Does Filling an SSD Reduce Its Lifespan?

While the lifespan of an SSD is related to write cycles, it’s typically measured by TBW (Terabytes Written). These values are rigorously tested by manufacturers, so under normal usage, it’s unlikely to exceed these limits. An SSD can last for 3-5 years without issues, by which time most users will be ready to upgrade to a faster, higher-capacity SSD.

You might have heard that keeping 30% of an SSD’s capacity free prolongs its lifespan. While this was true for early SSDs, modern SSD controllers come with wear leveling technology. This technology ensures all flash memory cells are used evenly, regardless of whether they contain fixed data. The algorithm automatically balances data distribution, ensuring optimal use of each storage cell.

Q4: Do SSDs Need Regular Defragmentation?

Like traditional HDDs, SSDs can experience speed degradation over time. For HDDs, this is due to increased file fragmentation, causing the read/write head to move more frequently, thus slowing down access times. Defragmentation helps by organizing files consecutively, reducing read/write times.

However, SSDs don’t have physical read/write heads, and the time to access any memory cell is the same. Defragmentation is not only unnecessary but also reduces SSD lifespan. Speed degradation in SSDs occurs because data must be erased before being rewritten. A new SSD doesn’t need this process, so it operates faster initially. Regular formatting can help maintain its speed.

Q5: Do PCIe 5.0 SSDs Overheat Easily?

Aside from cost, a significant issue with PCIe 5.0 SSDs is the substantial heat they generate during operation. Managing this heat is a major challenge for memory chip, controller, and SSD manufacturers.

While all hard drives generate heat, PCIe 5.0 SSDs, due to their small M.2 form factor and increased layer stacking, have limited surface area for heat dissipation. The significantly higher data transfer speeds and IOPS (input/output operations per second) also contribute to increased heat.

Temperature is critical to the lifespan and stability of computer components. Overheating can compromise the reliability of PCIe 5.0 SSDs and prevent them from achieving peak speeds. Manufacturers are developing various solutions to address this heat generation problem.

廢熱是 PCIe 5.0 SSD 目前的最大罩門,全速運作時得到 75 度以上的工作溫度,算是家常便飯。

Q6: What Cooling Solutions Are Available for PCIe 5.0 SSDs?

As mentioned, heat management is a critical issue for PCIe 5.0 SSDs. To ensure stable, long-term use and extend the lifespan of SSD products, manufacturers are exploring various cooling solutions.

Some companies add graphene heat dissipation stickers to SSDs, while others offer models with small heat sinks. There are also active cooling solutions, such as fan-based M.2 heat sinks similar to CPU coolers, significantly reducing SSD operating temperatures.

Motherboard manufacturers are also tackling this problem, with many high-end motherboards now featuring “heat armor” over M.2 slots to increase heat dissipation. However, if you purchase an SSD with an integrated heat sink, you may not be able to use the motherboard’s built-in heat armor. Choosing the right cooling solution for your SSD is crucial before purchase.

部分主機板廠商會為 PCIe 5.0 的 M.2 插槽設計額外的散熱器,可帶來更佳的冷卻效果。

Q7: Applications for PCIe 5.0 SSDs

Many consumers wonder about the practical applications of PCIe 5.0 SSDs’ high speeds. After all, PCIe 4.0 SSDs already offer speeds up to 8GB/s.

For everyday users, the performance gains from PCIe 5.0 SSDs may not be noticeable in daily system operations, as most tasks involve small, scattered files. Therefore, the perceived difference between PCIe 4.0 and 5.0 SSDs isn’t significant in typical use cases.

However, for users frequently loading and processing large files, such as video editors, engineers, or software developers, the advantages of PCIe 5.0 SSDs become more apparent. These SSDs can significantly reduce processing times for large files, providing a better work experience.

對於影片剪輯這類需要周旋於各種大型媒體檔案的工作情境,採用速度更快的 PCIe 5.0 SSD,就能得到更加高效率的操作體驗。

Q8: Benefits of PCIe 5.0 SSDs for Gaming

While PCIe 5.0 SSDs are primarily beneficial for creators, they also offer advantages for gamers. Modern games often require hundreds of GBs of storage. Faster PCIe 5.0 SSDs can significantly reduce game loading times, providing a smoother gaming experience.

Using Microsoft’s DirectStorage technology and GPU decompression capabilities, PCIe 5.0 SSDs can accelerate the rendering of high-resolution textures, reducing processor usage and allowing the system to handle more tasks simultaneously.

Q9: System Requirements for PCIe 5.0 SSDs

To experience the maximum speed of PCIe 5.0 SSDs, most users will need a major hardware upgrade, including the processor and motherboard.

Intel CPUs starting from the 12th generation and AMD CPUs from the Ryzen 7000 series support the PCIe 5.0 standard. Consumers must choose the latest CPUs from these brands to use PCIe 5.0 SSDs.

Motherboards are more complicated, as PCIe 5.0 signals are managed directly by the CPU. High-end motherboards typically have PCIe 5.0 expansion slots, either in M.2 or standard PCIe card formats, but not always both.

Lower-end chipsets and motherboards, even if compatible with newer Intel or AMD CPUs, often lack support for PCIe 5.0 SSDs or expansion cards. For example, entry-level AMD AM5 platform chipsets like the A620 do not support PCIe 5.0 slots, so consumers need to opt for B650 chipsets or higher.

Because motherboard support for PCIe 5.0 varies widely, consumers should confirm whether their chosen motherboard has PCIe 5.0 M.2 slots before purchasing. Alternatively, choosing flagship Z or X series motherboards can be a straightforward solution.

Q10: PCIe 5.0 SSD Compatibility

All PCIe 5.0 SSDs are backward compatible with previous PCIe standards, including PCIe 3.0 and PCIe 4.0. This means a PCIe 5.0 SSD will still work if installed in a PCIe 3.0 or 4.0 slot, though its maximum speed will be limited by the slot’s theoretical maximum, such as 8GB/s for PCIe 4.0×4.

Conversely, installing a PCIe 4.0 SSD in a PCIe 5.0 slot will allow the SSD to operate normally, but its speed will be limited by the SSD itself. PCIe’s generational compatibility reduces the risk of damage from incorrect installation. However, when installing PCIe 5.0 SSDs, prioritize the highest-spec slots on the motherboard to achieve the best data transfer speeds.

Q11: Should I Upgrade to a PCIe 5.0 SSD?

While PCIe 5.0 SSDs are becoming more common, their high cost means they often lack cost-effectiveness. Consumers prioritizing value should continue using PCIe 4.0 or 3.0 SSDs.

However, if you seek extreme performance and have or plan to build a next-generation system with Intel’s 13th or 14th generation CPUs or AMD’s Ryzen 7000 series or higher, and your motherboard supports PCIe 5.0 with integrated PCIe 5.0 M.2 slots, then PCIe 5.0 SSDs are worth considering.

In the foreseeable future, PCIe 5.0 SSDs will coexist with PCIe 4.0 and 3.0 SSDs. Consumers can assess their need for high-speed data transfer, such as for large file transfers, video editing, or gaming, to decide whether a PCIe 5.0 SSD is necessary.


SSDs offer significant advantages over traditional HDDs, including faster speeds, greater durability, and lower energy consumption. Whether for a gaming rig, professional workstation, or everyday computing, SSDs provide a noticeable performance boost. When choosing an SSD, consider your specific needs and budget to find the best option for you.

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