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A Complete Guide to Solid State Drive (SSD)

Solid-state drive or Solid-state disk, abbreviated as SSD, is a computer storage device made of integrated circuits.

You can use non-volatile memory (mainly NAND Flash in flash memory) as a permanent storage device, or use volatile memory (such as DRAM) as a temporary storage device.

Solid-state hard drives often use SATA, PCI Express, mSATA, M.2, ZIF, IDE, U.2, CF, CFast... and other interfaces. At present, due to the difference between the price per unit and the maximum storage capacity of the mechanical hard disk, the solid state hard disk cannot completely replace the mechanical hard disk for the time being.

How do SSDs Work? | How does your Smartphone store data? 


I What is Solid State Drive?

II SSD Classification

2.1 Solid State Drive based on FLASH   Memory

2.2 Solid State Drive based on DRAM

III Development History

IV SSD Basic Structure

4.1 Main Control Chip

4.2 Cache Chip

4.3 Flash Memory Chip

V Compare with Traditional Hard Disk

VI SSD Advantages and Disadvantages

6.1 SSD Advantages

6.2 SSD Disadvantages


I What is Solid State Drive? 

Solid State Drive, also called solid state disk or SSD, is a hard disk made from an array of solid-state electronic memory chips, consisting of a control unit and a memory unit (FLASH chips / DRAM chips). The interface specification and definition, function and usage method of solid state disk are identical to those of ordinary hard disk drive, and the product shape and size are also the same as that of ordinary hard disk drive. 

The working temperature range of SSD chip is very wide: Commercial product: 0~70℃; Industrial product: -40~85℃. Although the cost of manufacturing an SSD is high, it is still gradually being popularized into the DIY market. Due to the difference between solid state drive technology and traditional hard disk drive technology, there are many new memory manufacturers. Manufacturers only need to buy NAND memory, and then they can manufacture solid state disk with proper control chip. The new generation solid state drive generally uses SATA-2 interface, SATA-3 interface, SAS interface, MSATA interface, PCI-E interface, NGFF interface, CFast interface and SFF-8639 interface.

II SSD Classification

There are two kinds of storage media in solid state drive, one is FLASH chip and the other is DRAM.

2.1 Solid State Drive based on FLASH Memory

Solid state drive based on FLASH memory(IDE FLASH DISK, Serial ATA Flash Disk) is using FLASH chips as its storage media. Its appearance can be made into a variety of forms, such as: Laptop hard drive, Micro hard disk, memory card, USB flash disk and etc. The biggest advantage of this SSD is that it is movable, and the data protection is not controlled by power supply. Also, it can be applied to various environments, but its service life is not too long, so it is suitable for individual users. In a flash-based solid state drive, memory cells are divided into two categories: SLC (Single Layer Cell) and MLC (Multi-level Cell). 

Solid state drive based on FLASH memory

Solid state drive based on FLASH memory

The characteristics of SLC is its high cost, small volume and high speed. And for MLC, it is with characteristics of large volume, low cost but low speed. Each unit of MLC is 2bit, which is exactly twice as many as SLC. However, due to the large amount of data stored in each MLC storage cell and the relative complexity of the structure, the probability of error will increase, so the error correction must be carried out. This action will cause its performance to lag significantly behind the SLC flash memory with simple structure. In addition, the advantage of flash memory is that the number of duplicates is up to 100000 times, which is 10 times higher than that of MLC flash memory. In order to ensure the lifetime of MLC, the control chip is calibrated and the intelligent wear balance algorithm is used, so that the write times of each memory cell can be divided equally, and the mean time between failures (MTBF) can reach 1 million hours.

2.2 Solid State Drive based on DRAM

Solid state drive based on DRAM is using DRAM as the storage medium. However, its application range is currently narrow. It follows the design of traditional hard disk, which can be volume setup and managed by most file system tools of operating system, and provides industrial standard PCI and FC interfaces for connecting hosts or servers. The application can be divided into two kinds: SSD hard disk and SSD hard disk array. It is a kind of high performance memory and has a long service life. The downside of it is its need for independent power supply to protect the data security.

Solid state drive based on DRAM

Solid state drive based on DRAM

III Development History

> 1956: IBM invented the world's first hard disk.

> 1968: IBM restates the feasibility of Winchester technology, which established the development direction of hard disk.

> 1970: StorageTek developed the first solid state hard drive.

> 1989: The world's first solid state hard disk occurred.

> 2006.03: Samsung took the lead in launching a solid state hard disk laptop with 32GB capacity

> 2007.01: SanDisk released an 1.8-inch solid state hard disk with 32GB and 2.5-inch model with 32GB in March.

> 2007.06: Toshiba has launched its first solid-state hard disk laptop with 120GB capacity.

Intel SSD 520 Series

> 2008. 09: The official launch of MemoRight SSD marks the accelerated entry of Chinese enterprises into solid state hard disk industry. 

> 2009: With the development of SSD , all the manufacturers crushed into this industry , and the storage virtualization then entered a new stage .

> 2010.2: Magnesia released the world's first solid-state disk with SATA 6Gbps interface, which breaking through the speed of SATAII interface reading and writing(300MB/s).

> The end of 2010: Renice launched and patented the world's first high-performance mSATA solid state disk.

> 2012: Apple uses 512GB solid state hard drives on its laptops.

> 2015.08.01: TEKISM introduced the first mobile solid-state hard disk with Type-C interface. The SSD provides the latest Type-C interface and supports double-sided insertion of the USB interface.

> 2016.01.01: Chinese storage company TEKISM has released the world's first Type-C fingerprint encrypted SSD.

SSD M300

IV SSD Basic Structure

The FLASH based SSD is the main category of solid state drives. Its internal structure is very simple. The main body of the solid state hard disk is actually a PCB board, and the most basic accessory on this PCB board is the control chip, cache chip(some low-end disks have no caching chip) and NAND flash that used for data storage.

The more common solid state hard drives on the market are: LSISandForce, Indilinx, JMicron, Marvell, Phison, Goldendisk and Samsung. The main control chip is the brain of solid state hard drive. One of its functions is to reasonably allocate the load of data on each flash memory chip, and the other is to transfer the whole data and connect the flash memory chip with the external SATA interface. The ability of different master control is very different in data processing ability, algorithm, flash chip reading and writing control , which will directly lead to a ten times gap of solid state hard disk performance.

Different SSD

Different SSD

4.1 Main Control Chip

Table 1. Brand, model and product of the main control chip for solid state drive



Representativ eproduct

Autonomous optimizatio nsoftware


PC29AS21AA0,     PC29AS21BA0

Intel 320 Series     G3(80G)



SF-1500/SF-1200,     SF-2000 series

OCZ Agility3,     A-DATA S511/S510,ShineDisk



SF-2141, SF-2241     and SF-2281                                                    SF-2200/2100   series

A-DATA SP900,     Kingston HyperX series,                                                     ShineDisk



JMF602, JMF612,     JMF618, JMF667H Heracles

A-DATA SP600,     ShineDisk, Kingston SSD Now V series, GALAXY series



IDX110M00-LC,     IDX110M01-LC




88SS9174-BJP2,     88SS9174-BKK2

Intel 510     series, Micron C400, PlextorPX-128M2S, A-DATA SP920/SP910



S3C49RBX01-YH80,     S3C29RBB01-YK40

SAMSUNG SLC 3.5     100GB




TOSHIBA Q series




Goldendisk SLC     2.5 60GB



SM2242,SM2244,     SM2246 SM2235

KINGOOD 8G 16G     32G 64G128G series


Data Solution

NDS334FNDS334     series



PER820 series,     PER860 series

PER820 series,     PER860 series


4.2 Cache Chip

The cache chip is next to the main control chip. Solid state drive and traditional hard disk both require high speed cache chip to assist the main control chip for data processing. It is important to be noted here that there are some cheap solid state drive solutions to save the cost of the cache chip, which will have a certain impact on the performance in use.

4.3 Flash Memory Chip

Apart from main control chip and caching chip, chips on the other place on PCB board are mainly NAND Flash chips. NAND Flash memory chips are divided into SLC, MLC and TLC NAND Flash memory. 

V Compare with Traditional Hard Disk

The interface specification and definition, function and usage method of solid state drives are almost the same as those of ordinary hard disk, and the shape and size of solid state drives are basically the same as that of ordinary 2.5 inch hard disk.

Solid state drive has the advantages of fast reading and writing, light mass, low power consumption and small volume, which is not possessed by traditional mechanical hard disk. At the same time, its disadvantage is obvious. Although IDC believes that SSD is in the mainstream of the storage market, its price is still relatively high and its capacity is relatively low, once the hardware is damaged, the data is difficult to recover, and others think that the durability of solid state drives is relatively short.

The main factors that influence the performance of solid state drive are main control chip, NAND flash media and firmware. Under the same conditions, what kind of interface is adopted may also affect the performance of SSD.

The mainstream interface is SATA (including two kinds of interfaces for 3Gb/s and 6Gb/s) and the SSD of the PCIe 3.0 interface. Duo to the difference of the design and the principle of data reading and writing between SSD and the common disk, the internal structure of SSD is also very different. In general, the structure of solid state disk (SSD) is relatively simple and can be disassembled; therefore, most of the articles we see about SSD performance evaluation include an internal disassembly diagram of SSD.

On the other hand, the data reading and writing of the ordinary mechanical disk is to lift the magnetic head by the air produced by the high speed rotation of the disc, which makes the magnetic head infinitely close to the disk without contact, and the stepper motor is used to push the head to read the data of changing the track. Therefore, its internal structure is relatively complex, more sophisticated, which is generally not allowed to disassemble. Once human disassembly, there is a strong risk of damage on the disk and disk can not work properly.This is why disassembly diagrams are largely invisible when evaluating ordinary disks.

VI SSD Advantages and Disadvantages

6.1 SSD Advantages

6.1.1 Fast reading and writing

Using flash memory as storage medium, the read speed of SSD is faster than mechanical hard disk. SSD does not use (magnetic) head, and its seek time is almost 0. The speed of continuous writing is amazing, and most SSD manufacturers will claim that their solid state drives continue to read and write faster than 500MB / s! The speed of solid state hard disk is not only reflected in continuous reading and writing, but also in random reading and writing speed, which is directly reflected in most of the daily operation. Associated with this are extremely low access times, with the most common 7200 rotary mechanical drives running at 12-14 milliseconds, while solid state drives can easily reach 0.1 milliseconds or less. 

6.1.2 Shock resistance

Traditional hard drives are disk-type, data is stored in the disk sector. The solid state drive is made from flash memory particles (mp3, U disk, etc.), so there are no mechanical components inside the SSD. This will not affect its normal use even when moving at high speed or even with tilting, and minimize the possibility of data loss in the event of collisions and oscillations. Compared with the traditional hard disk, solid state drive has an absolute advantage.

6.1.3 Low power consumption 

The power consumption of solid state drive is lower than that of traditional hard disk.

6.1.4 Noiseless

Solid state drive has no mechanical motors and fans inside, thus it works with a noise value of 0 dB.Flash based solid state drives have lower energy consumption and lower calorific emissions (but the consumption of high-end or large-capacity products will be larger). There are no mechanical parts inside, so there will be no mechanical failure, no collision, no shock or vibration. Because the solid state hard disk uses the flash memory chip without mechanical parts, it has the characteristics of low heat emission and fast heat dissipation.

6.1.5 Wide range of working temperature

A typical hard disk drive can only work in the range of 5 to 55℃ and most solid state drives can work at -10~70℃. The solid state hard disk is smaller in size and lighter in weight than the mechanical disk of the same capacity. The interface specification and definition, function and usage method of solid state drives are the same as those of ordinary hard disk, and the product shape and size are the same as that of ordinary hard disk. The working temperature range of the chip is very wide(-40~85 ℃).

6.1.6 Lightweight

Solid state drives are lighter in weight, 20-30 grams lighter than regular 1.8-inch hard disks.

6.2 SSD Disadvantages 

6.2.1 Capacity

The maximum capacity of solid state drive is only 4TB. It is SanDisk Optimus MAX

6.2.2 Limited Service Life

Solid state drive flash memory has the problem of limitation of erasing times. 

A flash memory is completely erased once called a P / E, so the life of flash memory takes P/E units. The lifetime of the 34nm flash chip is about 5000 P / E, while the lifetime of the 25nm is about 3000 P / E. With the improvement of SSD firmware algorithm, the new SSD can provide less unnecessary writing. An 120GB solid state drive that writes 120GB of files to one P / E. In practical use, individual users often write in random rather than continuously. So there will be higher probability of bad sectors. In addition, while each sector of the solid state drive can be repeatedly erased 100000 times(SLC), in some applications such as LOG records in operating system , A sector may be read and written over and over again, in which case the actual lifetime of a solid state disk is not yet tested. However, with the equalization algorithm, the life expectancy of the memory unit is increased by 100000 writes, and the low cost MLCs have only 10, 000 write lives, while the cheap TLC flash memory is only 500 to 1, 000 times.

6.2.3 Expensive

The price of the 128GB solid state drive on the market is around RMB550, while the price of the 256GB is around RMB950 .


1. Is SSD better than HDD?

SSDs in general are more reliable than HDDs, which again is a function of having no moving parts. ... SSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs.

2. What is a solid state drive used for?

A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage.

3. Is a 256GB SSD better than a 1TB hard drive?

A 1TB hard drive stores eight times as much as a 128GB SSD, and four times as much as a 256GB SSD. The bigger question is how much you really need. In fact, other developments have helped to compensate for the lower capacities of SSDs.

4. Do I need HDD if I have SSD?

You don't need both but having a SSD for your operating system and a HDD for your storage drive might be the best bang for your buck. Otherwise, you only need one; a HDD is cheaper, larger, slower, and more prone to data loss. A SSD are normally smaller in storage for the same price but faster and shock resistant.

5. Should I upgrade to SSD?

It's time to upgrade to an SSD if you're still using a mechanical hard drive in your computer. ... Solid-state drives are so much faster because they don't have a spinning magnetic platter and moving head. After upgrading, you'll be amazed at the performance improvements and wondering why you waited so long.

6. What are the pros and cons of a solid state drive?

a. SSD is faster.

b. SSD can take a licking

c. HDD is cheaper; SSD is still expensive.

d. HDD has greater storage capacity than SSD

7. Do solid state drives crash?

SSDs can fail, but in a different way than traditional HDDs. While the latter often fail because of mechanical issues, SSDs may fail due to the methods used to write information. ... Each P/E cycle gradually degrades the memory of an SSD's cells until they eventually become worn down.

8. Can I put SSD and HDD together?

The answer is absolutely yes. You can install both, but, SSD will have faster SSD speeds and HDD will still have slower HDD speeds. It is an excellent idea to use SSD and HDD at the same time. An SSD boasts many distinctive merits such as fast loading speed, low power consumption, and etc.

9. How much faster is a SSD than a HDD?

As noted above,solid-state drives can read/write speeds of around 550 MB/s faster than a hard disk drive. SSDs can go even faster, provided your computer can handle it. A PCIe SSD can achieve anywhere from 1.2 GB/s to 2.2 GB/s - assuming you have a motherboard that can handle these speeds.

10. How can I tell if my SSD is failing?

So here are four signs of SSD failure:

Sign #1: Your computer takes a long time to save files.

Sign #2: You have to restart often.

Sign #3: Your computer crashes during boot.

Sign #4: You receive a read-only error.