What is an internal hard drive used for?

An internal hard drive is one of the most important components in a computer. It is used to store all of the data on the computer, including the operating system, software programs, and files created by the user. Without a hard drive, a computer would not be able to function beyond the temporary data held in its memory (RAM).

What is an internal hard drive?

An internal hard drive is a storage device that is installed inside a computer’s case on the motherboard. It contains one or more inflexible platters coated with magnetic material, arranged in stacks on a spindle. Data is written to and read from the platters using a read/write head that moves very quickly over the surfaces of the platters as they spin. The data is organized in concentric circles called tracks that are divided into sectors. Each sector stores a fixed amount of data, typically 512 bytes in modern hard drives.

Internal hard drives come in two main types: HDD (hard disk drive) and SSD (solid state drive). HDDs rely on mechanical moving parts – the platters and read/write heads. SSDs use integrated circuits and have no moving parts, making them faster, quieter, and less prone to mechanical failure. Both types connect to the computer’s motherboard using SATA, SAS or NVMe interfaces.

Internal hard drives come in a standard width of 3.5 inches for desktop computers and 2.5 inches for laptops. The larger the capacity of the hard drive, the more data it can store. Common capacities for internal hard drives range from 120GB to 10TB for HDDs and 128GB to 8TB for SSDs.

Storing the operating system

One of the primary jobs of the internal hard drive is to store the operating system. The operating system manages the computer’s hardware resources and provides services for software programs. Popular operating systems like Windows, macOS and Linux are sophisticated programs with many files that take up several gigabytes of space.

During the boot process, the computer’s BIOS or UEFI firmware loads data from the hard drive into the computer’s main memory to launch the operating system. The OS stays running in memory to manage tasks, while periodically accessing more files from the hard drive as needed.

Without the hard drive, the computer would not be able to load and run the operating system, rendering the computer useless beyond the limited functions of the firmware.

Installing and running software

Another vital job of the internal hard drive is to store software applications and games. From office suites like Microsoft Office to creative programs like Photoshop to PC games, all types of software get installed to and loaded from the internal hard drive.

When a program is launched, the operating system loads the necessary executable files, libraries, assets and other components from the hard drive into RAM where the program’s code can be accessed quickly and efficiently while running. As with the operating system, software depends entirely on the hard drive for non-volatile storage of its program data.

Storing personal files

Internal hard drives provide local and reliable storage for all the data a user generates and accumulates over time. This includes but is not limited to:

  • Documents – Word processing documents, spreadsheets, PDFs, etc.
  • Photos – Personal images from smartphones, digital cameras DSLRs, etc.
  • Video – Home movies, downloaded online videos, video captures from webcams or other devices.
  • Music – MP3s, streaming service downloads, ripped CDs, etc.
  • Downloaded files – Software installations, ebooks, miscellaneous data from the web.

Without adequate hard drive space, users would not have anywhere to store their growing personal data collections. The internal hard drive provides capacious, long-term storage right within the computer for immediate access without relying on external devices or network connections.

Caching and temporary files

In addition to storing long-term user data and installed programs, internal hard drives improve performance by supporting caching and temp files that come and go as needed during active computing sessions.

Web browsers like Chrome cache visited web pages onto the hard drive so they load faster when accessed again. Media players similarly cache songs or videos being streamed from the internet. Games cache game data for fast access during gameplay. The operating system caches recently accessed programs and data.

The computer also utilizes hard drive space to temporarily store system and program files that are only needed during an active session. These can include web browser cookies, application help files and so on. Temporary storage provides efficiency and snappiness as the computer avoids reloading things from scratch each time.

Without caching and temp file support afforded by ample internal hard drive space, the user experience would feel much slower and less responsive overall.

Supporting the paging file/swap file

Internal hard drives can be leveraged as additional memory (RAM) supplementation through the paging file or swap file. This is a dedicated file or partition that the operating system uses as virtual memory. When active programs and data exceed the amount of available RAM, less frequently accessed data gets written out to the paging file on the hard drive temporarily.

This helps the programs run smoothly despite RAM capacity being exceeded. When the data is needed again, it is simply read back into real RAM. This process is completely transparent to the user. Without the huge capacity of the hard drive available for paging/swapping, the computer would grind to a halt when RAM fills up.

Allowing for hibernation and fast boot times

Hibernation is a power-saving mode where the computer saves its entire state to the internal hard drive and fully powers down. Upon waking from hibernation, the full saved state is restored in seconds to exactly where the user left off.

Fast boot is when the computer writes key parts of the operating system image to the hard drive during shutdown to reduce boot times. Upon restart, it simply reloads the essential OS files instead of starting completely from scratch.

Hibernation and fast boot provide additional conveniences that would not be possible without the high capacities and relatively fast access speeds of modern internal hard drives.

Serving as a destination for backups

Users can utilize their internal hard drive space to store backups of their important files as part of a multi-pronged data protection strategy. Backup software can automate scheduled backups from system drives to a separate internal hard drive or partition.

Keeping backups on an internal drive that is distinct from the system drive provides protection from file corruption, accidental deletion, malware, drive failures and other scenarios that could otherwise lead to data loss.

Hosting virtual machines and containers

With abundant hard drive space available, power users can take advantage of virtual machines (VMs) that emulate standalone computer systems in software. VMs run guest operating systems and programs isolated from the main host environment.

For example, a Linux VM can be hosted on Windows. VMs provide flexibility for testing environments and running software not natively compatible with the host OS.

Containers are another virtualization method that depend on internal storage space to provide segregated, lightweight OS environments for running specialized applications in isolation.

Storing media collections

With terabyte-sized internal drives now commonplace, media enthusiasts are able take advantage of ample local space to store their personal media libraries onboard their desktop computers. This includes:

  • Music – Storing thousands of songs ripped from CDs, downloaded from iTunes or streaming services, etc.
  • Movies – Keeping digital movie purchases or ripped Blu-ray/DVD copies.
  • Photos – Amassing huge personal photo collections spanning years of memories.

Enthusiasts appreciate keeping their massive media collections on an internal drive for quick and reliable access without relying on external storage devices or streaming over the network.

Serving as scratch disks for video editing

Video editing applications like Adobe Premiere Pro use scratch disks to offload captured video footage while editing projects. Scratch disks provide high-speed temporary working storage so video can be edited smoothly during the workflow prior to final export.

By storing scratch data locally on an internal SSD or HDD, editors can work faster rather than being bottlenecked by slow external devices or network connections.

Providing abundant game storage

Modern game consoles come standard with hard drives in the terabyte range to accommodate their massive game file sizes, some exceeding 100 GB each. PC gamers similarly depend on expansive internal hard drives for storing games downloaded via services like Steam, Origin or Epic Games Store.

Gamers can keep their entire gaming libraries installed locally on an internal hard drive for lightning-fast access. External storage or deleting and re-downloading games would be much more inconvenient.

Storing Drivers

Internal hard drives store driver software to enable the operation of hardware components like integrated graphics card, network adapters, audio processing chipsets, printer ports, and other devices.

Without drivers installed to the hard drive, that corresponding hardware will be non-functional. Drivers encapsulate hardware compatibility and optimizations for the operating system to utilize.


In summary, modern internal hard drives are indispensable for PCs and laptops. They provide non-volatile storage capacity for permanent and temporary data of all kinds, including operating systems, software programs, personal user files, and system management files. Internal drives supply vast space for caching, paging, hibernating, fast booting, running virtual machines, storing huge media libraries, video editing scratch data, modern gaming, and running a computer smoothly through all typical usage scenarios and far beyond. When choosing a new computer, opting for a large, high speed internal drive will provide the best experience and enables truly harnessing the machine’s capabilities.