7 Technical Specifications of SSD Explained – The Complete Guide

By | January 24, 2021

SSDs have become the default storage media on laptops, and desktops compared to traditional hard drives.

They are available in multiple form factors like M.2 drives and 2.5" standard disk drives.

The standard disk drives are commonly used on desktops and the more compact M.2 ssds are used on all machines including laptops, desktops and mini pcs.

Like any other pc hardware component, ssds also have a lot of technical parameters associated with their capacity and performance that are worth knowing if you want to get the best ssd performance for your machine.

Some SSDs are meant for long term reliable storage in enterprise environments, whereas some are made to be cheaper and provide lots of storage for home users.

In this guide, we are going to give you a better understanding of solid-state drives (SSD) and how you can choose what is best for you.

Why is SSD better

SSDs are much faster compared to Hard Disks or HDDs. But what makes an SSD faster ?

Traditional hard drives are made of disk platters that spin at a certain speed for accessing the stored data.

Whereas, SSDs use flash memory chips that allow instant access to any memory location making them significantly faster. The same storage technology is used in usb flash drives, smartphone memory cards and many other solid state storage solutions.

Flash memories make SSDs faster as data is available in an instant for your computer to read, compared to an HDD that needs its disk platters to first spin and reach the location physically before it can find the data.

So fundamentally they use very different technologies but serve the same purpose.

Samsung 860 EVO Sata M2 SSD

Common Specifications

Now that you have an idea of what an SSD is, it is time to dive into technical specifications that you should know when shopping for a solid-state drive.

The common specs include

  • Form Factor
  • The Interface
  • Read Speed
  • Write Speed
  • Endurance Rating TBW - Overall Lifespan
  • IOPS
  • Storage Capacity
  • Memory Cell Type - SLC, MLC, TLC, QLC, PLC

1. Form Factors

First on our list is the SSD form factor. The most common solid-state drives come in a 2.5” or 7 mm configuration which is about the size of a traditional laptop hard drive.

On the other hand, newer versions of SSDs are about half the size of a single RAM stick called M.2 solid-state drives. The M.2 drives are bare circuit boards without any enclosure.

Common Form factors include:

  • 2.5" SSD Drive
  • M.2 Drive
  • Portable SSD

For example the Western Digital Blue SSD comes in both 2.5” and M.2 form factors with a wide range of storage capacity options.

Installing an M.2 ssd requires a M.2 PCI-e slot on your system. Modern desktop motherboards have M.2 slots where the drive can be installed directly.

However if you are planning to upgrade an old desktop that does not have a M.2 slot, then you should go for a 2.5" SSD drive that can be connected using a SATA cable.

Alternatively you could use M.2 PCI-e card to install M.2 drives on a desktop that don't have a dedicated M.2 slot on the motherboard.

Western Digital 2.5 inch SATA Solid State Drive

Western Digital 2.5 inch SATA Solid State Drive

If you are leaning towards mini-ATX builds, an M.2 SSD would come in handy for saving space on your system. M.2 drives are also a great option for laptops, given that it is supported by your laptop.

The M.2 drives also support the NVMe standard which makes them much faster than the SATA based SSDs. So if your system supports M.2 NVMe your first choice should be an M.2 ssd.

Besides these, there are the portable ssds as well that are smaller in size compared to the 2.5" drives and are connected to the system via usb

Samsung T5 Portable SSD

Samsung T5 Portable SSD

2. SSD Interface

Choosing the right interface for your SSD is also important as this can further improve the already fast performance of your drive. Given that solid-state drives are configured on two form factors, their transport interface is also different.

M.2 drives use a PCI-E slot on your motherboard for connection and the typical 2.5” solid-state drives use the traditional SATA connection, also used by hard drives.

To give you a better understanding of how these transport interfaces perform, following are the speeds:

  • SATA II - Maximum bandwidth of 3Gb/s or 384 MB per second.
  • SATA III - Maximum bandwidth of 6Gb/s or 768 MB per second.
  • PCI-E Gen 3 - Maximum bandwidth of 8GT/s or 8 GB per second.

Seeing the figures above, if you are aiming for the max performance possible, it is clear that opting for an M.2 SSD would help you achieve that goal.

Although most solid-state drives would not be able to max out that 8GB per second bandwidth, it would still perform a lot faster compared to SATA interface drives. The maximum speed of NVMe M.2 drives is around 3-5 GB/s.

More information on this wikipedia page

https://en.wikipedia.org/wiki/Solid-state_drive
https://en.wikipedia.org/wiki/NVM_Express

However, keep in mind that even a SATA SSD would be miles faster compared to hard disk drives.

3. Read Speed - Sequential and Random

Sequential read speed is the rating of how quickly large files can be accessed on your storage device when reading memory locations sequentially.

Random read speed indicates how fast can the ssd read random memory locations that are not in any particular order.

Faster read speeds would also mean faster file access and transfers, quicker loading times, and smoother performance when you are browsing through your files.

To give you an idea, a typical 7200 RPM hard drive would have a sequential read speed rating of 80-160 MB per second. When compared to an SSD, the Western Digital Blue has a read speed of up to 560 MB per second which is three times the performance of a traditional hard drive.

Moving to M.2 drives, its sequential read speed could vary between 2.4 GB per second up to 3.4 GB per second. That is a lot of performance!

4. Write Speed - Sequential and Random

Write speeds determine the amount of data that a storage device can take in every second.

Faster write speeds ensure that creating or copying large files and installing applications is fast.

In comparison, traditional hard drives would have a write speed of 160 MB per second, which is slow, compared to the 530 MB per second sequential write speed of modern solid-state drives.

However, it should be noted that random write speed is often much slower than sequential write speed, but still much faster than hard disks.

5. Endurance Rating (TBW - Terabytes Written)

While SSDs are more durable compared to hard drives, they can still break down in time. Flash memories can be written only at a certain number of times before they start to become unreliable. Since SSDs are made of flash memory, they can suffer from performance loss and even corruption.

In this case, you should look out for solid-state drives with a decent TBW (Total Bytes Written) rating. TBW indicates how much data you can write on an SSD over its lifespan.

A good SSD like the Western Digital Blue has a 600 TWB rating for the 4 terabyte model.

For better understanding, a 250 GB SSD would usually have a 70 TWB rating which you can max out for a year if you store 190 GB of new data every day, which is impossible for a typical user.

In this case, it is safe to say that most SSDs would have a lifespan of double or even triple compared to an ordinary hard drive in normal usage.

5. IOPS

When it comes to real-world performance, SSDs IOPS rating can help you in figuring out how it would really perform once it is installed on your system.

IOPS or Input/Output Operations Per Second determines how fast an SSD can read and write random packets of data like browser files, cookies, saved game data, and documents.

You can convert these read and write IOPS ratings to MB per second rating which gives you an idea of the amount of random data that an SSD can process.

For example, the Western Digital Blue SSD has a 4KB sequential read speed of 97,000 IOPS.

In order to convert these to MB per second, we would use the formula:

MBps = (IOPS * 4)/1024

So, our Western Digital Blue solid-state drive would have 378.90 MB per second 4KB sequential read speed. To put this in context, a 7200 RPM hard drive would have a 120 IOPS rating, which is less than 1 MB per second.

6. Capacity

Last is the storage capacity. Most SSD manufacturers offer solid-state drives with a capacity of 80 GB up to 4 TB or even higher. However, SSDs get even more expensive as you increase its capacity.

To put that in context, a 500 GB variant of Western Digital Blue SSD is priced around $60 while its 4 TB model would cost you over $500 on Amazon. For that price, you can already build a decent desktop PC.

7. Memory Cell Type - SLC, MLC, TLC, QLC

Solid-state drives use NAND flash memory that consists of cells that can hold bits of memory. These bits are controlled by an electric charge that either turns it off or on.

Although all SSDs use the same NAND flash memory, their performance differs from one model to another, depending on the type of cell used on the drive and the market that it is supposed to cater to.

For example the more expensive enterprise grade SSDs are made of SLC memory which support higher number of write cycles. As a result they have less storage space per unit space and per unit price.

On the other hand consumer grade SSDs meant for home users are mostly based on TLC or QLC which store more bits per cell and have fewer write cycles. But they also offer the higher amount of storage space per unit price.

Besides NAND Flash, there are other storage technologies like 3D Xpoint developed by Intel and Micron which are sold under the brand name of Optane. More details can be found here: https://en.wikipedia.org/wiki/3D_XPoint

To better understand the storage cell types, lets take a look at the features of each.

7.1 Single Level Cell (SLC)

Typically found on server-grade drives, single-level cell flash is known to be the most accurate when it comes to reading and writing data.

Being server-grade hardware, SLC flash memory is also known to be the most durable with an expected read and write cycle of up to 100,000.

However, there are also drawbacks from this type of cell configuration, like higher production cost that also reflects with its price on the market, and it is only available in smaller capacities for now.

Due to its high production costs, there are only a few drives with this NAND memory and they are really expensive. To put that in context, Intel’s X25-E SSD is equipped with an SLC NAND memory configuration and costs around $250 for a 32 GB storage capacity.

These are used mostly in enterprise environments like servers and real time systems.

7.2 Multi-Level Cell (MLC/eMLC)

Based on its name, multi-level cell memory stores multiple bits of data in one cell, which makes manufacturing cost a lot cheaper compared to SLC drives.

Having a low price, multi-level cell drive is not as durable as compared with SLC flash memories with an expected read and write cycle of only 10,000.

However, due to its affordable price, MLC drives are easier to get on the market and are really popular among average consumers.

The Samsung 860 EVO SSD is a good example of this setup which has a decent price of around $115 for its 1TB variant.

On the other hand, there is also another variant of MLC called eMLC which also uses multi-level cells but is optimized for enterprise usage.

Having better performance and reliability, eMLC solid-state drives are being used in industrial setups that require intense read and write cycles like servers. Drives equipped with this kind of NAND flash can last between 20,000 to 30,000 read and write cycles before it starts to become unreliable.

7.3 Triple Level Cell (TLC)

TLC solid-state drives can write three bits to each of its cells, which allows it to have higher storage capacities compared to MLC and SLC memories.

However, packing three bits on one cell has a few drawbacks like slower performance, decreased reliability, and endurance. But don’t get us wrong, TLC drives are still great, and it is also used for enthusiast-grade SSDs.

You can expect about 3,000-5,000 read and write cycles per cell with this type of NAND flash, which is really low compared to MLC and SLC flash memories.

On a positive note, TLC drives are the least expensive on the market and are still a viable option compared to mechanical hard drives.

7.4 Quad and Penta Level Cell (QLC/PLC)

Similar to how TLC flash memory works, Quad and Penta level cell NAND flash can store multiple bits in a single cell (four bits for QLC and five bits for PLC) but with a few compromises.

Since flash memory has a limited life span, storing larger bits to one cell can only make its life span shorter. While having larger capacities are its stronger points, reliability is one of the main issues when it comes to QLC and PLC NAND flash.

With a rating of only 1,000 read and write cycles, drives with this kind of flash memory should only be used for storing backups or as a game drive, which is still faster compared to traditional hard drives.

7.5 3D NAND Flash

Compared to traditional 2D planar NAND memory, 3D NAND stacks cells on top of each other, utilizing both vertical and horizontal space that resulted in better performance and increased reliability without needing to shrink single cells to its limits.

Having more cells means more storage. Thanks to 3D NAND memory, solid-state drives are now available in higher capacity variants with some manufacturers releasing up to 2TB M.2 drives like the Samsung 970 Evo Plus.

Currently, 3D NAND flash memories are offered on triple-level cell and multi-level cell configurations.

Conclusion

In summary, even the worst SSD on the market is guaranteed to be faster compared to mechanical hard drives. For a couple of bucks, an SSD is a great way to improve your system’s overall performance and would surely last longer compared to HDDs.

Now that you know the technical specifications of an SSD, you can shop for a storage drive that would best fit your needs.

Links and Resources

https://en.wikipedia.org/wiki/Multi-level_cell
https://en.wikipedia.org/wiki/Flash_memory#NAND_flash

About Silver Moon

A Tech Enthusiast, Blogger, Linux Fan and a Software Developer. Writes about Computer hardware, Linux and Open Source software and coding in Python, Php and Javascript. He can be reached at [email protected].

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