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<!DOCTYPE HTML> <html lang="en"> <head> <meta charset="utf-8"> <style id="antiClickjack">body{display:none !important;}</style> <script> if (self === top) { var antiClickjack = document.getElementById("antiClickjack"); antiClickjack.parentNode.removeChild(antiClickjack); } else { top.location = self.location; } </script> <meta name=viewport content="width=device-width, initial-scale=1"> <link rel="shortcut icon" href="/img/favicon.ico" type="image/x-icon"> <link rel="apple-touch-icon" href="/img/apple-touch-icon.png"> <link rel="stylesheet" href="/main.css" type="text/css">  <link rel="canonical" href="https://www.helpwithpcs.com/hardware/hard-drive-basics.php"> <meta name="description" content="A look at what a hard drive is, its basic operation, its performance specifications, the different hard drive capacities and also the interfaces in common use."> <title>Hard drive basics | Capacities, RPM speeds, interfaces and mechanics</title> </head> <body> <div id="top_outer"> <div id="header"> <div id="header_inn"> <div id="logo"><a href="/"><img src="/img/help-with-pcs.png" width="318" height="40" alt="Help with PCs" title="Click for our homepage"></a></div> <div id="hdr_srch"> </div> </div> </div> <div id="nav_outer"> <ul class="nav_mn"> <li class="nav"><a href="/hardware/" class="nav2">HARDWARE</a></li> <li class="nav"><a href="/software/" class="nav">SOFTWARE</a></li> <li class="nav"><a href="/internet/" class="nav">INTERNET</a></li> <li class="nav"><a href="/upgrading/" class="nav">PC UPGRADING</a></li> <li class="nav"><a href="/maintenance/" class="nav">PC MAINTENANCE</a></li> <li class="nav"><a href="/jargon/" class="nav">DICTIONARY</a></li> <li class="nav"><a href="/gaming/" class="nav">GAMING</a></li> </ul> </div> </div> <div id="wrapper"> <div class="c_container"> <div itemscope itemtype="http://schema.org/TechArticle"> <h1 itemprop="name">Hard drive basics | Capacities, RPM speeds, interfaces and mechanics</h1> <div class="cnt_hdr_box"> <div class="cnt_hdr_img"><img src="/hardware/img/hard-drive-basics.jpg" width="316" height="149" alt="hard drive basics" title="Guide to the basics of hard drives" class="mn_img"></div> <div class="cnt_hdr_txt"> In this guide we aim to give you an idea of just what a hard drive is. We cover what these ubiquitous devices are and their uses in today's world. <br><br> We then go on to explain hard drive capacities, RPM speeds and the interfaces used to connect them. We finish with a look at the internal components. </div> </div> <div class="gads_hdr"><div class="cnt_ad_undhdr_hdr">advertisement</div> <div class="cnt_ad_undhdr_ad"> <script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>  <ins class="adsbygoogle gads_hdr_res" data-ad-client="ca-pub-7821244969182905" data-ad-slot="2064534968" data-ad-format="auto"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <hr></div> <h2>What is a hard drive and what does it do?</h2> A hard drive is a mass storage device found in all PCs (with some exclusions) that is used to store data such as the operating system, installed software and a user's files. <br><br> The data on hard drives can be erased and/or overwritten. The hard drive is classed as a non-volatile storage device, which means it doesn't require a constant power supply in order to retain the information stored on it (unlike <a href="/jargon/ram.htm">RAM</a>). <br><br> There are two types of hard drives: <strong>electromechanical</strong> and <strong>SSD</strong>. <br><br> Electromechanical hard drives are the traditional type of hard drives, also known as spinning disks. They use mechanical parts to read and write data to the platters. The platters spin at a very high speed, usually 5400-7200 revolutions per minute (RPM), while the read/write heads move back and forth over the surface of the platters. The faster the RPM, the faster the hard drive can access and transfer data. <br><br> On the other hand, solid-state drives (SSD) are a newer type of hard drive that use flash memory to store data. Unlike electromechanical hard drives, <a href="/jargon/ssd-solid-state-drive.htm">SSDs</a> have no moving parts, making them faster and less prone to mechanical failure. Instead of platters and read/write heads, SSDs have a controller chip that manages the data stored in the flash memory. <br><br> Both types of hard drives perform the same basic function of storing and retrieving data, but they do it in different ways. Electromechanical hard drives are cheaper and have more storage capacity, but they are slower and less durable. SSDs are faster and more reliable, but they are more expensive and have less storage capacity. <hr> <h2>Hard Drive Capacities</h2> When it comes to hard drives, there are two main types available on the market: electromechanical hard drives and solid-state drives (SSDs). While both types store data, they do so in different ways, and as a result, their maximum storage capacities also differ. <br><br> In recent years, HDDs have seen a significant increase in their storage capacity. While the earliest hard drives had a capacity of only a few megabytes, modern electromechanical hard drives can store multiple terabytes of data. As of 2023, some of the largest electromechanical hard drives available have a capacity of up to 18 terabytes. <br><br> On the other hand, SSDs store data on flash memory chips, similar to those used in USB drives and memory cards. Unlike HDDs, SSDs have no moving parts, making them faster, more durable, and less prone to failure. However, SSDs are more expensive than HDDs, and their maximum storage capacity is currently lower. <br><br> As of 2023, the largest consumer-grade SSDs have a capacity of up to 16 terabytes. While this is lower than the largest electromechanical hard drives, SSDs are still the preferred choice for those who need high-speed access to their data or require a reliable storage solution. <br><br> Regardless of the type of hard drive, the storage capacity is measured in bytes, common capacities are stated in <a href="/jargon/megabyte.htm">MB</a> (Megabytes) and <a href="/jargon/gigabyte.htm">GB</a> (Gigabytes) and <a href="/jargon/terabyte.htm">TB</a> (Terabytes). It's important to note that there is a difference between the decimal interpretation and binary interpretation of these prefixes, which can lead to confusion for consumers. <br><br> Below shows the difference between the decimal and binary prefixes. <br><br> <table> <tr> <td style="text-align: center; width: 70px;"><b>PREFIX</b></td> <td><b>DECIMAL VALUE</b></td> <td><b>BINARY VALUE</b></td> </tr> <tr> <td style="text-align: center;"><b>MB</b></td> <td>1,000,000 bytes (1000<sup>2</sup>, 10<sup>6</sup>)</td> <td>1,048,576 bytes (1024<sup>2</sup>, 2<sup>20</sup>)</td> </tr> <tr> <td style="text-align: center;"><b>GB</b></td> <td>1,000,000,000 bytes (10<sup>9</sup>)</td> <td>1,073,741,824 bytes (1024<sup>3</sup>, 2<sup>30</sup>)</td> </tr> <tr> <td style="text-align: center;"><b>TB</b></td> <td>1,000,000,000,000 bytes (10<sup>12</sup>)</td> <td>1,099,511,627,776 bytes (1024<sup>4</sup>, 2<sup>40</sup>)</td> </tr> </table> <br> As you can see there is a large disparity between the values, especially as storage sizes get larger. For example, if you purchased a hard drive stating it had 300GB you may find that your software reports the storage capacity as only 279GB. <br><br> To avoid confusion, some software applications now use the binary prefixes MiB, GiB, and TiB to describe the storage capacity. However, these terms are not yet widely used. <br><br> In conclusion, modern hard drives have come a long way in terms of storage capacity, with electromechanical hard drives and SSDs offering massive storage capacities that were once considered impossible. As technology continues to advance, it's likely that we'll see even larger and faster hard drives in the future. <hr> <h2>Hard Drive RPM Speeds</h2> You will often see hard drives advertised as being capable of a certain RPM (Revolutions Per Minute). This figure (as the name suggests) refers to how many times the spindle makes a complete 360掳 turn in any single minute. <br><br> The higher the RPM, the faster the data can be read from the platters, which increases overall performance. RPM values range from about 5,400RPM to 12,000RPM and above. However, it's important to note that RPM speeds primarily apply to electromechanical hard drives, as solid-state drives (SSDs) operate differently. <br><br> Electromechanical hard drives, also known as traditional spinning hard drives, rely on a spinning disk or platters to read and write data. The RPM speed directly affects the performance of these drives. A higher RPM means that the platters spin faster, allowing data to be accessed more quickly. As a result, higher RPM drives generally offer faster data transfer rates and reduced latency. <br><br> RPM values for electromechanical hard drives typically range from about 5,400RPM to 12,000RPM and above. The choice of RPM speed depends on factors such as storage capacity, intended usage, and desired performance levels. Higher RPM drives, such as those spinning at 7,200RPM or 10,000RPM, are commonly used in desktop computers, gaming consoles, and servers where faster access to data is critical. Meanwhile, lower RPM drives, such as 5,400RPM variants, may find applications in less demanding environments or budget-friendly systems. <br><br> In contrast, SSDs are a different type of storage technology that does not rely on spinning platters. Instead, they use flash memory to store and retrieve data. As such, SSDs do not have RPM speeds because there are no mechanical parts involved in data access. Instead, their performance is primarily measured by their read and write speeds, typically expressed in megabytes or gigabytes per second (MB/s or GB/s). <br><br> Compared to electromechanical hard drives, SSDs offer significant advantages in terms of speed and reliability. SSDs are known for their lightning-fast access times and high transfer rates, as they don't require physical movement to retrieve data. This results in faster boot times, reduced application load times, and snappier overall system responsiveness. <br><br> Due to their inherent differences, electromechanical hard drives and SSDs are suited for different use cases. Electromechanical hard drives still excel in scenarios where large storage capacities are required at a more affordable price point, such as mass data storage or archival purposes. On the other hand, SSDs are ideal for users seeking enhanced performance, responsiveness, and durability, making them popular choices for operating systems, frequently accessed applications, and demanding tasks like video editing or gaming. <br><br> In summary, while RPM speeds are a relevant metric for electromechanical hard drives, they do not apply to SSDs. Electromechanical drives with higher RPM values generally offer improved performance due to faster data access from spinning platters. On the other hand, SSDs leverage flash memory and deliver exceptional speed and reliability without RPM limitations, making them a preferred choice for users seeking enhanced performance in their storage solutions. <hr> <h2>Hard Drive Interfaces</h2> Hard drives are available with a number of different interfaces, these interfaces provide connectivity and facilitate communication between the hard drive and the rest of the system. <br><br> The various interfaces each have their own specifications. <h3>IDE (Integrated Drive Electronics)</h3> IDE was a popular interface in the past, but it has largely been superseded by SATA due to its slower data transfer rates. However, IDE hard drives are still used in some older systems. <h3>USB (Universal Serial Bus)</h3> <a href="/jargon/usb.htm">USB</a> is a common interface used for connecting external hard drives to computers. Although the actual interface on the hard drive is typically SATA, a USB-SATA bridge facilitates communication between the drive and the system. <h3>SATA (Serial Advanced Technology Attachment)</h3> <a href="/jargon/sata.htm">SATA</a> has become the most commonly used interface in modern desktop computers and laptops. It offers much faster and more efficient data transfer than IDE and is generally the preferred choice for most systems. <h3>SCSI (Small Computer System Interface)</h3> <a href="/jargon/scsi.htm">SCSI</a> was a popular interface for power users and performance-critical devices, but it has largely been replaced by SATA. However, SCSI devices and interface cards are still available, and recent adaptations such as Serial Attached SCSI (SAS) and USB Attached SCSI (UAS) have made it easier to connect SCSI devices to newer systems. <h3>NVMe (Non-Volatile Memory Express)</h3> NVMe is a newer interface designed specifically for solid-state drives (SSDs) that uses a high-speed PCI Express (PCIe) bus for faster data transfer. NVMe is becoming increasingly popular in high-performance systems. <h3>Thunderbolt</h3> Thunderbolt is a high-speed interface that supports data transfer rates of up to 40 Gbps, making it ideal for use with external hard drives and other devices that require fast data transfer. It uses a USB-C connector and is commonly found in newer Macs and PCs. <h3>Fibre Channel</h3> Fibre Channel is a high-speed interface commonly used in enterprise-level systems for connecting storage devices to servers. It offers fast data transfer rates and is designed to provide reliable and scalable performance in large-scale environments. <hr> <h2>Hard drive mechanics (electromechanical)</h2> The mechanical technology used inside electromechanical hard drives hasn't changed that much over the years, in fact the basic mechanics in today's hard drives are much the same as they were 10 or 15 years ago. <br><br> <div class="cnt_img_left"><img src="/hardware/img/hard-drive-tutorial/hard-drive-mechanics.jpg" width="250" height="198" alt="Hard Drive Mechanics"></div> <div class="cnt_img_txt"> In <b>fig 1.1</b> to the left you can see the internal mechanics of a hard drive: <br> <ul> <li><b>A</b> - Platter/s <li><b>B</b> - Read/Write Head/s (and slider) <li><b>C</b> - Actuator Arm/s <li><b>D</b> - Actuator <li><b>E</b> - Spindle </ul> </div> <hr> <span class="emph">Platters</span> (A in fig 1.1) <br> Most Platters are made of either an aluminium/alloy or glass/ceramic composite and are like glass to the touch. There is always more than one platter inside modern hard drives and each platter is double sided (with some exceptions). <br><br> In modern hard drives the platters spin at 5400RPM and above. The distance (flying height) between the read/write heads and the platter is around 50nm (0.05µ, a human hair is around 100µ). <br><br> You should never open your hard drive's sealed casing (unless you are in a controlled environment such as a clean room) as a single speck of dust is bigger than the gap between the platters and read/write heads. If dust/debris does enter the drive, it can have catastrophic results when the heads crash into it. <br><br> The platters have a magnetic coating which allows them to store the data magnetically. <hr> <span class="emph">Read/Write Head/s</span> (B in fig 1.1) <br> These are attached to the end of each actuator arm and as the name suggests they are responsible for reading and writing data to and from the platters. There is <i>usually</i> a set of read/write heads on each side of each platter although some drive configurations have an odd number of heads. <hr> <span class="emph">Actuator Arm/s</span> (C in fig 1.1) <br> Actuator arms move across the platters to position the read/write heads in the right place to read or write the required data. The actuator arms are manufactured so they have a spring action causing them to close if there is no platter present, this ensures they do not move away from the platter with time. As the drive winds up to full speed the air that is generated by the spinning motion lifts the sliders (and therefore the heads) around 50nm (0.05µ) above the platters. <hr> <span class="emph">Actuator</span> (D in fig 1.1) <br> This refers to the device that physically moves the actuator arms. Years ago they used to use stepper motors for controlling the actuator arms, but the problem with stepper motors in applications such as this is that over time and with a lot of use, they lose their integrity and can cause data corruption. <br><br> Another problem with stepper motors is that when they get hot (which hard drives do) they lose their precision. For example, data that is saved with a cool drive can sometimes be unavailable when the motor gets hot due to this displacement effect. <br><br> Stepper motors also required the read/write heads to be parked (moved to a data-free area of the drive). If the read/write heads were not parked and the drive suffered any shock (such as transportation), the data could be corrupted. <br><br> Nowadays most (if not all) hard drives use a voice coil instead of a stepper motor, unlike stepper motors, voice coils are linear and don't suffer from the same integrity problems. <br><br> Because voice coils are magnetically driven by electrical currents there is no mechanical wear and tear. Voice coils also negate the need for parking the heads before shutting off the power, as when they lose power the heads return to the parked position automatically. <hr> <span class="emph">Spindle</span> (E in fig 1.1) <br> The spindle revolves the platters, when you see an RPM (Revolutions Per Minute) specification of a hard drive it is referring to the spindle speed. <hr> </div> <div class="gads_bott"><div class="cnt_ad_bt_hdr_bott">advertisement</div> <div class="cnt_bt_ad_bott"> <script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script> <ins class="adsbygoogle gads_bt_res" data-ad-client="ca-pub-7821244969182905" data-ad-slot="3563024169" data-ad-format="auto"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <hr></div> </div> <div class="rh_col"><div class="cnt_ad_bt_hdr">advertisement</div> <div class="cnt_bt_ad"> <script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-7821244969182905" data-ad-slot="7470663368" data-ad-format="auto"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div></div> </div> <hr class="social"> <div class="sco"> <div class="social"><a href="https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="facebook"><img src="/img/social/facebook.png" width="42" height="42" alt="fb" class="social"></a></div> <div class="social"><a href="http://twitter.com/share?url=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="twitter"><img src="/img/social/twitter.png" width="42" height="42" alt="tw" class="social"></a></div> <div class="social"><a href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="linkedin"><img src="/img/social/linkedin.png" width="42" height="42" alt="ld" class="social"></a></div> <div class="social"><a href="http://www.reddit.com/submit?url=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="reddit"><img src="/img/social/reddit.png" width="42" height="42" alt="rt" class="social"></a></div> <div class="social"><a href="http://www.digg.com/submit?url=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="digg"><img src="/img/social/digg.png" width="42" height="42" alt="dg" class="social"></a></div> <div class="social"><a href="https://plusone.google.com/_/+1/confirm?hl=en&url=https%3A%2F%2Fwww.helpwithpcs.com%2Fhardware%2Fhard-drive-basics.php" rel="nofollow" target="google_plus"><img src="/img/social/google_plus.png" width="42" height="42" alt="gp" class="social"></a></div> </div> <hr class="social"> <div id="ftr_outer"> <div id="ftr_inner"> <div class="back_top"> <hr class="wh"> <div class="ftr_lnks"><a href="#top_outer" class="wh">back to top</a></div> </div> <hr class="wh"> <div class="ftr_lnks"><a href="https://www.helpwithpcs.com/advert-form.php" class="wh">Advertising</a></div> <div class="ftr_lnks"><a href="https://www.helpwithpcs.com/contact-us.php" class="wh">Contact us</a></div> <div class="ftr_lnks"><a href="https://www.helpwithpcs.com/copyright-information.html" class="wh">Copyright</a></div> <div class="ftr_lnks"><a href="https://www.helpwithpcs.com/disclaimer.html" class="wh">Disclaimer</a></div> <div class="ftr_lnks"><a href="https://www.helpwithpcs.com/privacy-policy.html" class="wh">Privacy policy</a></div> <div class="fix"></div> <hr class="wh"> <div class="ftr_lnks">© Copyright 2001-2024 HelpWithPCs.com</div> <div class="fix"></div> <hr class="wh"> </div> </div> <script> var _paq = _paq || []; _paq.push(['trackPageView']); _paq.push(['enableLinkTracking']); (function() { var u="//www.wdgsystems.co.uk/analytics_pk/"; _paq.push(['setTrackerUrl', u+'piwik.php']); _paq.push(['setSiteId', '3']); var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; g.type='text/javascript'; g.async=true; g.defer=true; g.src=u+'piwik.js'; s.parentNode.insertBefore(g,s); })(); </script> </body> </html>