what is solid state drive (SSD)?


What is solid state drive?

You could be wondering, what is solid state drive (SSD)? The simplest definition you can get about Solid state drive is it is a NAND flash memory device that has near instance access time and zero moving parts. The past several decades of computer evolution used the hard disk drive for storage purposes.  The hard disk drives have parts that moved mechanically and hence they were and still are undoubtedly susceptible to failure.

what is solid state drive (SSD)?

Solid state drive (SSD) storage devices perform the same function as the ubiquitous hard drives. However, SSD stores data in several flash memory chips that are interconnected. The flash chips are able to carefully retain data even when power is turn off.  However, this flash memory chips are quite different from the USB flash drives you and I use today. SSD chips are faster and are created with a higher degree of reliable that your USB thumb drive. This is the reason why SSD storage devices are more expensive that thumb drives even when they have equal storage capacities.

History and emergence

You may be thinking that SSD technology started the other day. You are wrong.  In fact, the experimentation on this type of storage protocol is almost as old as the transistors themselves. Solid state drives have been used in super computers in as early as 1970s and 1980s, while scientists started experimenting on them as early as 1950. However, you will not be surprised to realize that the technology was prohibitively expensive. The storage capacity was as big as 20 MBs, yes you read that correctly, 20 MBs. Their prices were 5-digits. Though it was occasionally used in the aviation and military sectors, they only appeared in consumer computers in the 1990s.

Later the prices started to drop because of the massive inventions and innovations in the hardware.  Despite their high prices, SSD storage devices had a seriously problem with the lifespan.  The approximate lifespan of an SSD was approximately 10 years.  However, in the 2000s, improvement in technology caused impressive upgrade on reliability and speed. They can now be used for more than 10 years now with a very good speed. This is how reliable SSD are today.

Different types of SSD

We cannot answer what is solid state drive (SSD) completely without looking into their different types. We can compare the SSD to random Access memory (RAM) only that the former uses NAND flash cells to save data while the former uses magnetic platter. The SSD controller stores the address of blocks so that files can be retrieved easily and instantly. The read and write for the SSD storage is done is nanoseconds.

While the computer random access memory (RAM) and the SSD storage uses ships, the two operates differently in you computer. The SSD flash is used for storage purposes whereas the RAM performs calculation of data retrieval from HDD, or SSD storages.

SSD form factor

You might not know what us form factor in computers. Form factor refer to size, shape and specification of the hardware.

SSD provided manufacturers with enough flexibility such that there are several diverse form factors. there are many solid state form factors. The one commonly available in the market is the 2.5-inch SSD. This for factor comes in multiple height that allows it to be used via SAS, SATA and NVM express protocol. A non-profit organization, the storage networking industry association, has pointed out to us that there are form factors.

Traditional HDD form factor

The first form factor is the traditional HDD. This enables SSD to physical fit in the SATA and SAS slots of PCs and servers.


The second form factor is PCI express. The SSD storage coms as cards so that it can be used as an add-in the PCs as the graphic cards are used. This type of the PCIe form factor as the name indicates are fitted in the PCIe slots of the motherboards.  The SSD storage are known for their high-speed performance since they do not network host bus adapters. In this category are the U.2 SSD which might replace the mini-SATA drives very soon.

The DIMM form factor.

DIMM stands for dual inline memory module.  The other name of DIMM is the NVDIMM (non-volatile dual in-line memory module). This form factor uses the SATA interface and other interfaces that common HDD can use.

M.2 form factor

M.2 form factor  is the newest SSD protocol. The M.2 SSD storages comes in various lengths. They are most referred to as NVMe (non-volatile memory express). The smallest is 4.2 cm while the longest M.2 SSD is 11.cm. what is fascinating about the M.2 form factor is that they are also plugged directly to the motherboard just like the PCIe. Because of their proximity to the motherboard, they become too hot. A lot of heat reduces not only the performance of m.2 SSD devices but also their stability. Many uses this form factor only for capacity expansion. M.2  slots may be missing in older small form factor computers.


Read more on what is small form factor (SSF)?.


As we have seen before, there exist several SSD form factors and so do their types. The type of SSD storage is categorized based on the NAND cell technology. So, based on the NAND cell technology, the following types of SSD storage are born;

Single level cell (SLC)

in this technology, each bit is stored in its cell. Therefore, it is not necessary to keep tabs on where the electron is located since only a 1 or 0 is being stored. What is necessary for this type of technology is to precisely control the follow of voltage.

Multi-level cell (MLC)

this type of SSD storage has two bits stored in each cell. It is therefore necessary to keep close tabs on the location of the electrons. Unlike the single level cell, voltage control is very complex. Insulation is necessary to prevent migration of electrons.

Triple level cell(TLC)

SSD storage now have three bits in every cell. Insulation is necessary to prevent migration of electrons. It is important to keep tabs on the location of electrons since their migration have more advanced effect on TLC than it is with SLC and MLC.

Quad level cell (QLC)

What is QLC flash and what workloads it is good for? SSD storage of this category have 4 bits in every cell. Insulation is necessary to avoid migration of electrons.  This type of SSD storage are most suitable for read-centric workloads. Well cited research has shown QLC wear out more when they are used for writing purposes other than reading.  When the data is written and deleted frequently, insulation is known to wear out very fast

Failure and reliability
Ssd vs hdd
Ssd vs eMMC
Purchasing consideration