Technology Explained

101 Guide To Solid State Drives

Aaron Peters 28-11-2017

Welcome to MakeUseOf’s Solid State Drives 101. In this guide we’ll take a look at the the latest, greatest mass storage device and:

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  • Compare them to other forms of mass storage media;
  • Examine how they work;
  • Look at the different types available, and;
  • Highlight elements of their operation and maintenance you should know.

Here is everything you’ll find in this guide.

1. Introduction to Solid State Drives

2. A Short History

ROM Chips| Hard Disks/Hybrid Drives | Flash Memory | Modern SSDs

3. The Anatomy of the SSD


Cells | Controller

4. Other SSD Specs You Should Know

Memory Type | Physical Interface | Logical Interface | Form Factors

5. How to Care For and Feed Your SSD


(De)fragmentation | The TRIM Command | Operating System Support

6. SSDs Are One of the Best Upgrades

Let’s dive in then, shall we?

1. Introduction to Solid State Drives

Computer mass storage has improved considerably since the days of punch cards (and their arch-enemies, flying insects). The computer industry survived the pains of moving back and forth through cassette tapes and swapping out floppy drives From Punch Cards to Holograms - A Short History of Data Storage Let's take a look at some of the technologies that shaped modern data storage, as well as where we go from here. Read More to single-write CDs. We now enjoy the convenience of large, fixed hard disk drives and rewritable optical media CDs Are Not Forever: The Truth About CD/DVD Longevity, "Mold" & "Rot" The digital age has revolutionized the way we handle information. Never before could humankind record and store so much information and in such diversity. While the amount of data has increased exponentially, the predicted life... Read More .


101 Guide To Solid State Drives ssd 101 history

But throughout these times, one form of storage — RAM Everything You Need to Know About RAM & Memory Management RAM is your computer's short term memory. Hence, memory management has a significant impact on system performance. Here we explain how RAM works and whether you can do anything to increase its efficiency. Read More  — has always been faster. Its advantage is that it accesses its data electronically, not mechanically. It suffers from one major drawback: it loses any data it holds when the machine powers down. It’s also more expensive on a per-byte basis. But a goal of the industry has long been for persistent storage to be more like RAM in terms of speed and robustness.

Developments in flash memory eventually produced Solid State Drives (SSDs), which marry the large(r) capacity and persistence of hard disc drives (HDDs) with the durability and (some of the) speed of flash memory. Let’s take a look at how SSDs came about, from both the technological and user experience viewpoints.

2. A Short History

While hard drives are obviously one parent of modern SSDs, they also owe some of their lineage to non-mechanical storage. The following all contributed, either in spirit or through technology, to today’s solid state drive.


2.1 ROM Chips

101 Guide To Solid State Drives Rom amiga39
Image Credit: Wikimedia Commons

Nowadays we usually hear of Read Only Memory, or ROM(s) in the context of flashing them to a mobile device What Is Rooting? What Are Custom ROMs? Learn Android Lingo Ever had a question about your Android device, but the answer had a bunch of words in it that you didn't understand? Let us break down the confusing Android lingo for you. Read More . Back before even mechanical hard drives were commonly available, computers would boot off of code stored in a ROM chip on the motherboard. As the name implies, your computer could only read from this medium. It would do so to load the initial “command prompt” from which you’d launch programs. As the capacity of these chips grew, they could hold entire operating environments like Amiga’s Workbench. They’re not quite the same as SSDs since they’re not writable, but they do represent the idea of running your OS off of non-mechanical media. Even modern EEPROMs, which you can write to, are still different since you can’t change their contents at runtime.

2.2 Hard Disk Drives/Hybrid Drives

HDDs obviously contributed to the development of SSDs, since most of the latter still use the same, or similar, hard drive standards. It made for a very easy transition from HDDs to SSDs when connection types like SATA (more on this later) make it simple to swap out an old mechanical drive for something faster. This path was made all the smoother by hybrid drives like Apple’s Fusion Drive What is Apple's Fusion Drive & How Does It Work? Solid state drives are awesome. The only snag is that solid state storage is still prohibitively expensive for storing lots of data. The days of cheap SSDs are probably not that far away, but for... Read More , which added some fast solid state storage to regular hard drives.

101 Guide To Solid State Drives 478px FCM vs
Image Credit: Wikimedia Commons

When flash-based storage first came on the scene it was expensive. This meant it not only cost a lot, but most likely offered very little space. Manufacturers took one of two routes to marry more HDD space to the faster SSD storage:

  • One approach would utilize solid state and supplement it with hard drive space. This could be a user purchasing both an SSD and hard drive, and installing programs or storing files where it made the most sense (e.g. performance-intensive apps like video editors on the better performing SSD, and less critical ones like a text editor on the HDD). There were also devices that combined both types of storage in the same physical unit, i.e. a 2.5-inch drive that housed both a mechanical HDD and solid-state storage. However these still appeared to the computer and OS as though they were two separate drives.
  • Alternately, there were also more integrated examples of the above where the mechanical and solid-state storage were in the same device, but it looked like a single storage device. These devices would cache frequently-used data in the SSD portion of the drive, so it could be served to programs faster. Either the drive’s controller hardware, the OS, or both would manage what data goes where. This gave you the speed of an SSD where it could be managed, and the capacity of an HDD overall.

2.3 Flash Memory


A lot of the removable media in the 1980s through early 2000s were not so different from HDDs. Examples include writable CDs (which used optical writing instead of magnetic) to items like Iomega’s “ZIP Drive” (basically a floppy disk that approached HDD capacity). They one and all involved some sort of mechanical innards, either in the drive, the medium, or both. As portable computing really started to take hold, along with serious digital photography, more resilient forms of media appeared. Compact Flash (CF) cards were one of the first 10 Things To Know About Digital Camera Memory Cards Over the past ten years of the digital photography revolution, digital camera memory cards have become increasingly more affordable and larger. Read More , and were joined by Sony Memory Sticks, MultiMedia Cards (MMC), Smart Media, eXtreme Digital (xD) cards, and the Secure Digital (SD) family.

These were some of the first flash-based memory, readily available for consumers, that were cost-effective and useful. They were device-dependent, however, so when the “thumb drives” USB Flash Drive Guide: 5 Things to Know When Buying One USB flash drives might seem mundane and straightforward, but there are a few tips and quirks that you should know before you buy your next one. Read More that started popping up in the early 2000s, they were a significant upgrade. They were just as portable, fast enough that most users wouldn’t notice the difference, and most importantly used the ubiquitous USB port. While they couldn’t match other media in cost per MB, they represented a cheap and effective way to carry your documents around with you, for example.

2.4 Modern SSDs

A couple of factors played into the uptake of modern SSDs over HDDs or hybrid drives. Firstly, the smartphone revolution raised people’s demand for portability. After all, if you could view a full web page on your phone, why shouldn’t you be able to have a light, convenient laptop to go with it? But the memory used in those portable machines also had an effect. If your phone can hold gigabytes worth of data without heavy, loud mechanical drives or ever rising temperatures, why shouldn’t a laptop be able to do it too?

Today’s SSDs have a number of distinct advantages versus HDDs, as follows:

  • Because there’s no moving, mechanical parts, when reading/writing data to a drive you’re just doing so electronically, which is very fast compared to a physical arm moving around.
  • It also means that these drives are much more resistant to bumps and drops damaging them.
  • The lack of moving parts eliminates the need to power those parts, saving battery life.
  • The reduction in power consumption comes with a reduction in heat, which helps your machine’s performance and extends the life of your motherboard.

But how do they convey these benefits? How do SSDs actually work? In the next section we’ll take a look at the internal workings of an SSD drive, and the differences between the different models.

3. The Anatomy of the SSD

ssd 101 hdd vs ssd
Image Credit: Partition Wizard

If you were to open up an SSD drive, you wouldn’t see the shiny platters and delicate actuator arm you get with a mechanical hard drive. Instead, what lies between the covers is a circuit board with a number of chips attached. There are many parts enclosed in those chips, but two that are key to understanding how SSDs work are cells and the controller. Let’s take a look at them in detail.

3.1 Cells

The basic unit of storage in an SSD is the cell. This is basically one (of many) compartments on the memory chip that contains a transistor capable of holding an electric charge. Its ability to hold this charge after power is removed sets it apart from your computer’s RAM. But otherwise, they’re similar.

ssd 101 cell values

Each of the cells holds a small electric charge that represents data, and when the bits are all put together they make up your files. Like hard drives though, these individual bits may live within various cells around the drive (i.e. not necessarily all contiguous cells). The same occurs in HDDs as well. But the major difference is no mechanical head needs to physically skip around the drive picking up all these bits to access a file. The SSD controller can gather quickly through electrical signals, which is why read speeds (and write speeds for that matter) are much faster compared to HDDs.

The below image illustrates how an SSD cell might store a simple text file (containing the letter “m”).

ssd 101 text as binary

3.2 Controller

While the cells actually hold the data, the controller interprets the presence or absence of the electric charge as zero or one values. It’s also responsible for the exchange of that data with the host operating system. The controller actually houses a host of functions, as shown in the below image.

ssd 101 controller

It’s sufficient for most purposes (unless your purpose is to become an electrical engineer) to know that the controller sits in between the host OS and banks of memory cells, and shuffles data between them. The above is a simplified view of how data gets from its place on the drive to your favorite application. There are lots of additional factors (like the use of pages and blocks How Do Solid-State Drives Work? In this article, you'll learn exactly what SSDs are, how SSDs actually work and operate, why SSDs are so useful, and the one major downside to SSDs. Read More ) that contribute to the safe and efficient storage of your cat videos. A manufacturer’s controller is where they’re able to add their value, by providing unique features or the best version of those shown above.

But the memory type and controller aren’t the only factors in how well an SSD performs. We’ll dive into some of these other features and specs of solid state drives in the next section.

4. Other SSD Specs You Should Know

When considering an SSD (or a machine with one pre-installed), it’s wise to know the features and what value they provide. The following sections explain some of the main attributes of SSDs, some of the options available, and touch on some of their pros and cons.

4.1 Memory Type

101 Guide To Solid State Drives ssd 101 tables flash type

In the examples above, the type of memory we’ve been describing is “flash memory,” specifically NAND Flash. NAND Flash is the same sort of memory used in removable media such as SD cards, as well as the memory in your phone or tablet. In fact, many of those mobile devices use SSDs of a particular form factor, which we’ll look at in a little bit. An alternative to this is DRAM-based SSDs, which use the same technology present in most RAM modules. While it boasts higher performance, it is very expensive, and also requires a way around DRAM’s issue of losing its contents when the power’s off. (This is accomplished by maintaining power when the machine overall is powered down, and/or with batteries.) Servers, and specifically those serving up performance-intensive applications, are the main use of DRAM. The SSDs found in the devices you’re likely to encounter are of the NAND type.

ssd 101 slc mlc diagram
Image Credit: Cactus Technologies

NAND Flash SSDs use one of two main types of cell formats. The first, Single-Level Cell (SLC), can only store one level of electric charge. So if the cell is charged, it equates to a value of one for a bit, and if not charged it equates to zero. Multi-Level Cell (MLC) drives can store two bits by supporting more than one charged level. A third type, Tri-Level Cell (TLC) can store three bits, although it’s not as common as SLC and MLC. Because it only has one level to support SLC is the more durable. You can effectively double your storage with the same amount of cells with MLC, so it’s cheaper. Bear in mind though, you may be writing to those cells up to twice as much and wearing the drive out faster.

4.2 Physical Interface

Another factor to consider in your SSD selection is how it’s connected to the system. In the case of mobile devices, you won’t have a choice in this matter. The manufacturer will have one of these physical interfaces as part of their design for the laptop, tablet, or phone. But you should still be aware of it, in the event that you’re weighing between devices using different interfaces. If you’re putting together your own machine How To Build Your Own PC It's very gratifying to build your own PC; as well as intimidating. But the process itself is actually quite simple. We'll walk you through everything you need to know. Read More , or upgrading a drive How to Move Windows from HDD to SSD to Improve Performance A Solid State Drive upgrade really improves performance. But how can you squeeze a large Windows installation onto a tiny SSD? Windows users can comfortably migrate from HDD to SSD in very little time. Read More in an existing machine, you may have one or more of the following different connections available. Based on what cables or slots you have you can buy SSD that best suits your needs.

Modern hardware provides two main interfaces to storage PCIe vs. SATA SSDs: Which Storage Drive Is Best? PCIe SSDs are faster than SATA SSDs. But you might not need it. This article explains how PCIe SSDs differ from SATA SSDs. Read More , including SSDs:

  • Serial ATA (SATA), which offers comparatively lower throughput speeds of 6 Gbps. But most motherboards will come with two or more of these, meaning you have some flexibility in designing your system. You could, for example, put your operating system and programs on an SSD while saving a larger, cheaper HDD for media storage. They’re also hot-pluggable, so if you need a blazing fast backup solution, an external SATA drive is a great choice.
  • PCI Express (PCIe), which offers extremely high throughput rates of 31.5 Gbps. However, PCIe form factor is a slot on the motherboard. You may also need to forgo a dedicated graphics card, as these also use a PCIe slot. PCIe cards sub-types refer to how many “lanes” are present, where a lane is a pair of pathways, one for sending and one for receiving. The designations “x1,” “x2,” “x4,” “x8,” and “x16” indicate how many of these lanes are in the card. The image below shows a motherboard with four PCIe slots: x4, x16, x1, and x16 from top to bottom. (The very last slot is a “legacy” PCI slot.) More lanes means more simultaneous transfers, but at a cost of higher power draw when all those lanes are full. There is also a “Mini PCIe” for smaller devices.

ssd 101 pci sizes
Image Credit: Wikimedia Commons

Two other interfaces compatible with SSDs are Fibre Channel, and Serial Attached SCSI (SAS). But these are server technologies, that (for example) connect giant pools of drives together to appear as a single resource. Unless you’re a server admin you’re unlikely to encounter these.

4.3 Logical Interface

101 Guide To Solid State Drives ssd 101 tables logical interfaces

Interfaces like SATA and PCIe are physical interfaces, and define what the hardware of a cable does. Logical interfaces define a standard set of functions that storage devices offer to the operating system. They don’t specify how the manufacturer should actually make those functions happen, only that they need to be available for the device to be compliant.

Here are three common logical interfaces in use with consumer SSD systems:

  • ATAPI: A much older standard developed for hard disks and other HDD-like media.
  • AHCI: A newer standard for devices using the SATA bus. While it does provide some benefit to SSDs, it was designed for spinning platter-based media. It does some things less efficiently for SSDs, creating bottlenecks.
  • NVMe: A standard specifically designed for SSDs. It takes advantage of properties such as multiple command queues. This means the controller can process multiple read/write commands instead of one (the case with AHCI).

This is a highly technical property of your device. What’s important for you to know 7 Terms You Need to Know When Buying a New SSD While SSD specifications may seem overly daunting at first, the truth is that these terms are quite simple to understand. Read More is that if your device uses a PCIe-based SSD, it should also support NVMe to get the best performance.

4.4 Form Factors

A last consideration in selecting an SSD is the form factor. As with interfaces, what device you’re buying for will make a big impact on this decision. Again, if you’re looking at a tablet or handheld device The Challenges of Installing a Tablet ROM: Why Is It So Hard? Changing the operating system on your PC is almost as easy as inserting a bootable USB and hitting install. But what about your tablet? It isn't the same -- or as easy. Read More , you’re stuck with what the manufacturer gives you. Laptops may or may not be the same. Some models give you easy access to the hard drive 5 Things to Know Before Upgrading Your Laptop Hardware If you're thinking of upgrading your laptop's hardware, there are a few questions you should ask yourself before diving in. Upgrading may not be the answer! Read More so you can replace it, in which case you’d better know what size drive you’ll need. Desktop machines may have a selection to choose from.

The PCIe models come as “cards” and not “drives,” and look not unlike other cards you may install 5 Things You Have to Know Before Buying a Graphics Card Here are five key points to keep in mind before you buy your next graphics card, otherwise you may regret your purchase. Read More . They’ve got a connector on the bottom, and lots of chips and diodes and stuff on the circuit-board.

101 Guide To Solid State Drives 640px Intel P3608 NVMe flash SSD PCI E add in card
Image Credit: Wikimedia Commons

The most recognizable of these will be the ones that use the same form factors as HDDs. These SATA models come in 1.8″ (second from the top in the below image) and 2.5″ (third from the top) sizes are readily available for both mobile and desktop machines. There are also 3.5″ drives (bottom) for desktops.

101 Guide To Solid State Drives ssd 101 sata drives
Image Credit: Tom’s Hardware

The top drive in the above image uses the mSATA form factor. It’s an example of devices suiting more specialized use cases, as follows:

ssd 101 msata vs m2
Image Credit: Wikimedia Commons

  • mSATA is a card-based format common in devices like tablets and extremely thin notebook computers. The newer M.2 form factor is an evolution of the mSATA standard, and uses more of a “blade” configuration to maximize usage of space. The above image shows an mSATA (left) and an M.2 (right) card side-by-side.
  • Module-based drives package a small SSD drive into a housing designed to plug directly into the motherboard (shown in the image below). While generally available, they target specialized PCs such as those used on industrial shop floors.

ssd 12

Now you understand the differences between the various SSDs on the market. And maybe you’ve even purchased one, or a device that contains one. Is there anything you need to do differently? Any special processes to keep it running correctly? Let’s take a look.

5. How to Care For and Feed Your SSD

By and large, things that apply to regular hard drives also apply to SSDs in terms of making sure they run well. Try not to drop them if you can help it. Don’t get them wet. Don’t let them overheat.

But there are some special considerations to be aware of.


As we showed in the above sections, the physical construction of SSDs is quite different from older disc-based storage. As a result, some of the things required to maintain an HDD don’t apply. The most obvious of these is defragmentation. This is the process that tries to move the blocks storing the data for your files closer together. The closer together the blocks for a file are, the less the mechanical arm needs to skip around to read them and re-assemble the file in memory.

SSDs, of course, don’t have this mechanical arm. So from the performance perspective, whether or not defragging your SSD will provide any benefit is something of a question. But remember also that SSD cells can withstand only a certain number of writes before they’ll fail. That’s why several of the authors here at MUO recommend 3 Top Tips To Maintain Performance & Extend The Life Of Your SSD For years, standard hard drives have been the speed limiting factor in overall system responsiveness. While hard drive size, RAM capacity, and CPU speed have grown almost exponentially, the spinning speed of a hard drive,... Read More against Top Tools for Managing and Maintaining Your SSD Did your SSD start out Usain Bolt fast, but now limps along? You can whip your drive back into shape using a handful of toolkits and optimization software, but caveat emptor: Some SSD optimization software... Read More defragmenting your SSD. Which stands to reason: if it provides doubtful gains but potentially damages the drive, why risk it?

The TRIM Command

What you should do, however, is make sure you’re using the TRIM command regularly. Like HDDs, even if you deleted a file from your OS it may still exist on the drive. It’s common that the value (charge) in that cell will remain until there’s another file that needs the space. But one unique aspect of SSDs is that they must be empty before they’re wrritten; in other words, a “rewrite” is actually a “erase-write.” If a file save operation needs to first erase all those cells before writing to them. This takes time, and results in slower perceived drive performance.

The TRIM command will identify all these “unused” cells and erase them by discharging them. In this sense it’s a kind of like the SSD’s version of “garbage collection” (getting rid of the contents of unused cells), secure delete How to Securely Erase Your SSD Without Destroying It SSDs can only be written to a limited number of times. Then how can you securely erase your SSD? Here's what you need to know! Read More (making those cells unrecoverable), and defrag all in one. You (or your OS) should run TRIM periodically to make drive operations faster. As a result, you should make sure you have proper support for it Why TRIM is Important to Solid State Hard Drives? [Technology Explained] Read More in your operating system, which is a convenient segue into the next section.

Operating System Support

101 Guide To Solid State Drives ssd 101 tables os support

Because SSDs connect to the machine over standard physical interfaces, modern OSes recognize them from the get-go. SATA drives should appear exactly like another hard drive. On the other hand, PCIe drives may show based on their logical interface, as is the case in Linux. As shown in the below image, my XPS 13’s disk printout clearly shows NVMe-based partitions. (These display as /dev/nvme with partition numbers afterwards).

101 Guide To Solid State Drives ssd 101 df nvme

What’s most important is whether it supports the TRIM command, and fortunately modern OSes do. TRIM support is actually a function of the filesystem, but filesystem support is dependent on the OS and its kernel One Size Doesn't Fit All: Why Software Isn't Universally Compatible Software is the same on any operating system, right? Wrong. It might look the same, and function similarly, but it is different behind the scenes. Read More . The table at the start of this section summarizes the OSes, and which filesystems compatible with those OSes, support TRIM.

SSDs Are One of the Best Upgrades for Your Laptop, Desktop, or Server

Hopefully this guide has given you a good idea of the many benefits of solid state drives over older hard disk drives. Here at MUO we’ve called an SSD “one of the best upgrades you can make” on several occasions. In particular, some reasons you might want to consider it include:

  • If you have an old desktop machine that’s showing its age, consider adding an SSD. Installing the OS and programs on this drive will yield dividends in a much quicker boot time and program performance. And don’t worry, you can still use your old HDD to hold all your pictures, music, and documents.
  • The above also apply to older laptops. You’ll also see an increase in battery life, and you’ll be better protected if you drop your device. Just make sure you can access your laptop’s drive bay, and that you’re buying the right form factor and interface.
  • If you run a server, either at home or for a small company, an SSD will better serve your users. In particular, the multiple command queues of PCIe-based drives can attend to concurrent request to share files and/or access applications.

What do you think? Are you an “all-SSD, all the time” type of person? Or have you used an SSD to take over for an HDD that still performs “cold storage” duties? Any stories about how an SSD upgrade changed your life? We want to hear all about it in the comments below!

Related topics: Hard Drive, Hardware Tips, Longform Guide, Solid State Drive.

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  1. Franky Edder
    December 15, 2018 at 10:21 pm

    I have a Dell Laptop. It came with an HDD with Windows 10 as the OS. Hard Drives and Windows move at a glacial pace, compared to the SSD I installed. I threw Windows out the window, and now use Debian Linux 9.5.

    Between the SSD and Debian, boot up time is faster than I've ever seen on any machine. SSDs are now getting less and less expensive. I saw a 1 TB SSD for less than $200. CD. I wish I could remember where I saw it. Crucial, Kingston, and a few other purveyors of memory have SSDs. As my Hillbilly Cousine would say "Go on an gitcha one."

  2. SSD
    January 4, 2018 at 9:16 am

    This article is perfect! 10/10.

    • Aaron Peters
      January 11, 2018 at 3:47 pm

      Thanks very much, appreciate it!

  3. dragonmouth
    November 28, 2017 at 2:45 pm

    I use a 40 GB SSD for the O/S and a 1TB HDD for non-O/S files. Unfortunately, since putting my O/S on an SSD, I have not seen the promised speed-up in boot times.