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Understanding HDD: A detailed exploration

Thankfully, it’s not hard to truly understand hard drives and you can make better decisions about your computer’s storage if you do. This handy guide promises to unlock all the basics for you. What do hard drives do exactly? How do they work and how big is big enough? Then choose specialized optimization technology like Avira System Speedup to help keep your computer clean, fast, and running smoothly. 


Welcome to storage 101! What is a hard disk drive? 

As the name implies, a hard drive—also known as a hard disk drive—is a hardware component that stores all your digital content. From pictures, music, and videos to your programs, operating systems and even your application preferences, if you’ve created, saved, downloaded, or installed it, it will find a home in your device’s hard drive.    

Here are some words and acronyms you’ll often hear in relation to hard drives and computer storage in general. It’s helpful to debunk them now so it’ll be easier to understand how hard drives work later: 

Non-volatile and volatile storage: This refers to storage devices that maintain their stored data even when they’re switched off. It’s also called static storage or static memory. Hard disk drives are non-volatile storage. The opposite of this is, of course, volatile storage (or volatile memory) which stores data when the computer is on but erases it immediately when the computer is off. RAM is volatile storage. So, be careful if you’re using a PC and the power is suddenly cut! The data in volatile storage will be gone.  

HDDs and SSDs: We devote a section to this later, but here’s a heads-up. HDDs are hard disk drives and the “opposite” are not soft state drives (as logical as this sounds) but solid state drives or SSDs. Both are storage devices, but they look and work differently. SSDs are newer, faster, use flash memory and are called “solid” because they don’t contain moving parts. There are also SSHDs which are a hybrid of both models.  

SATA: Hard drives are located in the drive bay and are connected to the motherboard via an Advanced Technology Attachment (ATA), Serial ATA (SATA), or another format. Without this interface, the hard drive couldn’t send information back and forth, so it would be living in splendid isolation. Great ATAs and SATAs are famed for their speed and capacities.  

“Gigs”, “megs”, and more: It’s all about size on a hard drive. Everything that’s stored here is measured in terms of file size—from small megabytes (MB) to larger gigabytes (GB) and finally vast terabytes (TB). Text files are typically tiny whereas image files are larger and music files larger still. Videos tend to be the biggest of all. Are you a video editor or is Microsoft Word your playground? What you’re most likely to store on your computer will be your best indicator of how much storage you’ll need.  

Some things never change though: Every computer needs at least one storage device to permanently hold data, which is why hard disks (or other formats, like SSDs) are essential.  

How do hard drives work? 

Imagine a traditional record player. Hard drives work on a similar principle, except they read (and write) magnetic charges instead of physical indentations. Record turntables may have inspired the developers of the first hard disk drives—and hard drives contain a similar spinning platter, but it has a thin magnetic coating. An actuator arm with a magnetic “head” moves over the platter and changes the pattern of magnetized particles beneath it. This head is just nanometers from the platter and the particles have different magnetic polarities which represent either a 0 or 1 in binary code. As the arm moves, it writes series of 0’s and 1’s as tiny areas of magnetic north or south. To retrieve that data later, the head goes to the same spot, recognizes the north and south spots whizzing by, and reads the stored 0’s and 1’s. This is more complicated than it may seem, as data is spread out randomly (this is called “fragmented”) across the platter.  

There’s always a delay when information is retrieved because the arm must move to the correct spot on the spinning platter to locate a specific piece of data. It may then have to repeat this process several times until it’s assembled all the data in RAM (your machine’s temporary storage) that’s needed for a particular file or application to open. This lag is called latency and it’s usually measured in milliseconds, but this might stretch to whole seconds with an older machine, if it’s clogged with junk, or powering up from rest mode. By contrast, today’s central processing units (CPUs) operate much faster, in nanoseconds. One nanosecond is equal to one million milliseconds (and suddenly the current men’s 100m world championship seems to have slowed to a crawl). All computers have a CPU or “brain” which executes processes and instructions by tapping into the data stored in RAM. With each generation, CPUs have become even faster. They’re now literally leaving hard disks eating their digital dust as HDDs struggle to retrieve data quickly enough and pop it into the RAM for processing. Hard drives tried to keep up by spinning faster and faster but eventually maxxed out at around 100,000 revolutions per minute. That probably deserves a round of applause, but it does display the limitations of HDD technology in an ever-faster and more demanding digital world.  

What does HDD storage look like? 

If you see a metal box, you’ve found your computer’s hard drive. It’s also helpfully labelled as a hard disk drive or HDD and houses the platter/s and actuator arm. As these are delicate physical mechanisms, they need to be protected from damage. If you open this metal casing, you’ll see the platters look like circular disks and are made of either aluminum, glass, or ceramic. They’re positioned inside a spindle connected to a motor that allows the platters to spin. The chamber also houses the magnetic read/write heads.  

The HDD form factor refers to its physical size and follows a set of industry standards that determine length, width, and height (plus the position of the interface connector). These guiding rules help ensure that HDDs are compatible with different computers. Form factors are given in inches and show the approximate diameter of the platter within the drive enclosure. To give you an idea about sizes: Desktop HDD form factors tend to be 3.5 inches while mobile form factors are 2.5 inches.  

What is the history of HDDs? And where are they headed? 

They were dreamt up by IBM and dominated the market for nearly 30 years. The first hard drive was produced in a California laboratory in 1956. It was called the IBM Model 350 Disk File and was as big as a large cupboard, with 50 24-inch disks inside that could store (wait for it) …5MBs of data! In 1980, IBM unleashed its fridge-sized IBM 3380 which tipped the scales at 250 kgs and could store a whopping 2.52GB. The trend for “bigger is better” continued into the ‘80’s but thankfully these were for huge, mainframe computers only and no-one was expected to commute to work carrying one. In fact, entire rooms were set aside for computers in those days.  

The ‘80’s weren’t just about XL computing sizes though. Smaller hard disk drives started to appear for the first personal computers. The earliest drives installed in these machines were 5MB in size with a form factor of 5.25 inches, so HDD shrinkage was already well underway while performance expanded. in 1990, hard drives could easily hold around 40MB, with more expensive options able to store more than 100MB. 

HDD form-factor size has continued to decrease as the technology evolves while density has skyrocketed. In 2021, drive manufacturer Western Digital unveiled two 20 TB HDDs! In 2023 hard drives up to 22TB were readily available. And this expansion is showing no sign of slowing down. The American data-storage specialist, Seagate Technology, has reportedly predicted 50+ TB HDDs for 2026—and the IT world is buzzing with hopes of 100TB hard drives by 2030. We shall see… 

The continuous evolution of hard drive technology today 

Exciting leaps in technology have driven the changes in the size and capacity of hard drives. In 2012, it turned out that air was so last century as helium-filled hard drives floated onto the scene. Helium offers many advantages over air as it’s less dense, plus cooler and lighter than air, so it reduces drag on an HDD’s spinning platters. Drives filled with helium therefore consume less power and offer greater performance. Plus, helium molecules are smaller, so disks filled with them generate much less noise. It really is a win win (win, win…). 

Who thought that the shingles on a roof would inspire an increase in storage density? In 2013, the first hard disk drives with shingled magnetic recording (SMR) technology appeared. In SMR, the magnetic tracks on each disk are layered over each other to save space, instead of sitting next to one another.  

In IT, as in life, change is the only constant and the evolution of hard drives continues unabated. Heat-assisted magnetic recording (HAMR—and pronounced “hammer”) is the next big thing. It greatly increases the storage capacity of HDDs by using a nanoscopic laser diode attached to the read/write head. This laser temporarily heats the disk during writing, which makes it more magnetic.  

Only time will tell if the industry has exhausted all the options for hard disk density enhancements. As you’ll have noticed by now, capacity is a top priority for HDDs, and this proved to be useful weapon in their arsenal as they faced a new storage rival: SSDs.  

The next step in storage: SSDs and what’s the difference to HDDs? 

SSDs and HDDs are both storage devices, but they work in very different ways. Instead of a mechanical spinning disk with a moving head, a solid state drive is a new generation of storage that uses flash-based memory, making it much faster than traditional HDDs. Data is stored permanently in an integrated circuit where it’s written, retrieved, and deleted electronically, with no need for moving parts. That’s why SSDs aren’t just fast—they’re also smaller, lighter, and quieter.  

Today, SSDs rule supreme in almost all new laptops and desktop computers. They’re particularly popular for businesses that process vast data volumes and need fast data-access times. Gamers love them too because games launch, and levels load faster when installed on an SSD. And if you carry around a laptop, you’ll appreciate an SSD. It has lower power requirements and is also shock resistant. 

Are HDDs right for you? The benefits and drawbacks of hard disk drives 

HDDs are no contender for SSDs if speed, ruggedness, and less noise are your top priorities. A hard disk drive could still be your winner though if a lower price tag and larger capacity are important. These users should consider traditional hard disks: 

  • Budget buyers: SSDs are simply too expensive for low-budget, entry-level machines. 
  • Heavy video downloaders and multi-media enthusiasts: You’ll need lots of space for these huge files and can easily get 8 TB or more cheaply. SSDs get expensive quickly for big video and music collections. 
  • Professional video/photo editors and engineers: You’ll fill up and wear out storage much more quickly than most, and replacing or adding a hard drive is cheaper than replacing a smaller SSD.  

SSDs are becoming more affordable but those looking for terabytes of storage that don’t need to be ultra-fast can still benefit from an HDD—at least for the foreseeable future. HDDs are the reliable workhorse for heavy loads and often have a longer life expectancy than their “flashier” cousin. SSDs will eventually fail because flash can only withstand a limited number of read/write cycles. When you hit that limit, their time is up. 

The rough guide to storage capacity: How much do you need?  

We’re consuming more media than ever these days and operating systems are taking up more space too. Can you ever have enough storage—and how much is enough? Whether you’re buying a new computer or just getting a new drive, understanding how much storage you need is an important guide. 

  • Do you use your computer mainly for web browsing and light productivity tasks, and don’t store large amounts of media on your device? Recommended storage: 256 GB 
  • Do you use programs that are more resource-intensive like Adobe Photoshop and Lightroom, and store medium to large numbers of photos, videos, and other files on your computer? Recommended storage: 512 GB 
  • Are you an avid gamer and/or use your computer to create and store high-resolution files—or do you need a lot of space for backup and redundancy? Recommended storage: 1 TB+ 

Remember that all storage products offer less memory capacity on your computer than stated on the box because of discrepancies in how these figures are calculated. Whatever storage you opt for, you can make the most of it with careful maintenance and regular clear-outs. Optimization tools like Avira System Speedup can help—and read on for more tips below. 


How to improve hard disk performance 

Slower startups and performance…longer load times…screen freezes and crashes. These are just some of the symptoms that you’re running out of disk space. If you’re concerned with your PCs performance, you can monitor it with a CPU stress test. A good rule of thumb is to keep 15%-20% free storage space on your HDD. It’s easier to achieve this, and keep your PC running smoothly, with regular hard drive maintenance. Follow these top tips:  

  1. Defrag your hard disk drive. This reorganizes the data so that it’s sequential and can be found and read more quickly. Follow these steps to defragment your Windows 10 PC 
  2. Enable disk write caching. This allows applications to run faster by temporarily storing the data-write requests to RAM instead of the disk. By delaying writing files to the hard disk, you can help improve file transfer speeds. Follow these steps to enable disk write caching 
  3. Clear unnecessary data to free up space and help improve storage performance. Delete apps you don’t use and consider moving large files to cloud or external storage.   
  4. Clear junk files. Temporary internet and system files, installer files, broken registries…over time this digital clutter can build up and slow your computer system down. And remember to empty the recycle bin! To delete temporary files, type “disk cleanup” in the search box on the taskbar. Then select “Disk Cleanup.” Choose the drive you want to clean and hit OK. Under “Files to delete,” select the file types you want to remove. Hit OK again and your computer will be a little cleaner.  
  5. Keep your entire computer system free from viruses and other malware. In addition to severely compromising your data and privacy, malware can wreak havoc on your machine’s performance. Learn how to help keep your hard drive and its contents safer by creating a data vault 

If you really want to wipe the entire slate clean, you can format your hard drive—but be sure to first read this step-by-step guide to formatting your hard drive the right way 

What are external hard drives, and do you need one? 

Most hard disk drives are found inside a computer. If you’re looking to expand the storage capacity of your machine or want to back up data to a portable device, external hard drives are a handy option. They connect to PCs or laptops through interfaces like USB 2.0, USB-C or via External SATA (eSATA). Beware that external hard drives may have slower data transfer rates than their internal HDD cousins. Depending on your priorities, they make up for this with their portability. You can store data from multiple devices and physically bring that data with you. And if anything were to happen to your computer or your hard drive fails your external storage may save the day. From damage caused by liquids, power surges, or drops, to malware running rampant or a clueless human accidentally deleting files that are critical to hard disk functionality—hard drives can and do fail. Reliable data backups are essential. Cloning the hard drive is also an option for the very security conscious.  

Explore specialized optimization tools for a faster, healthier machine 

Over time, hard drives become cluttered, and this digital junk eats away at storage space and slows the computer down. A specialized cleaning tool like Avira System Speedup helps optimize your machine for greater speed, accelerated starts, and smoother performance. In just a few clicks you can help banish the stuff you don’t need—from temp files to unnecessary user data. And for advanced cleaning tools, plus a battery extender and restoration options, see the Pro version.  


Will hard disk drives stand the test of time? Given the ambitious releases of ever-larger drives, HDD companies like Seagate certainly don’t seem to believe that this traditional technology is dying. As long as data centres are crying out for ever-larger amounts of storage and greater storage densities at lower costs, the future looks bright for this storage technology. The original IBM hard disk giant would be proud.  

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Freelance Cybersecurity Writer
Nicola Massier-Dhillon is an experienced cybersecurity and technology writer. Nicola spent many years as a senior copywriter and creative lead in marketing agencies, crafting compelling content and campaigns for major tech brands like HP, Dell, and Microsoft. She originally hales from Namibia and is a passionate advocate for the conservation of wild habitats--also putting her words to work for charities, eco-tourism, and healthcare. Nicola spends her time looking after her (wild) twins, rescue cats, and a crested gecko called Giles.
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