When it comes to computer storage, hard disks are one of the most common and widely used options. Hard disks come in two main forms – internal hard disks that are installed inside a computer, and external hard disks that connect to a computer externally through a USB port or other connection.
Quick Answers
In general, external hard disks use the same underlying technology as internal hard disks. The main differences are:
- External hard disks are portable and can connect to multiple computers, while internal hard disks are installed semi-permanently inside one computer.
- External hard disks get power through the USB or external interface cable, while internal hard disks connect directly to the computer’s power supply.
- External hard disks typically use smaller 2.5″ disks, while internal hard disks often use larger 3.5″ disks.
- External disks often have protective casings and rugged designs for portability, while internal disks mount into the computer case directly.
However, in terms of the core technology used to store and read/write data, external and internal hard disks rely on the same principles of magnetically recording data onto quickly rotating platters. The main components like the platter, head, and motor are essentially the same between external and internal hard drives. So while there are some practical differences in form and function, the underlying storage technology works similarly.
Internal Hard Disk Design
An internal hard disk drive is designed to be installed semi-permanently inside a computer. It mounts directly into the computer case and connects to the motherboard and power supply inside the system unit. Here are some key components and characteristics of internal hard drive design:
- 3.5″ form factor – Most internal hard disks use the larger 3.5″ form factor, which refers to the width of the platter inside the drive. 3.5″ platters can store more data with higher capacity hard disks.
- ATA interface – Internal hard disks connect to the computer via an Advanced Technology Attachment (ATA) interface, which provides a direct connection to the motherboard’s data bus.
- Spindle speed – Internal hard disks spin at speeds between 5400 RPM to 15,000 RPM, with faster spin rates enabling higher data transfer speeds.
- Cache memory – Internal hard disks contain a small amount of fast DRAM cache memory to buffer frequently accessed data.
- Firm mounting – Internal hard disks mount securely into drive bays with integrated power/data connections.
With these design elements, internal hard drives are engineered to reliably operate at fast speeds to access programs and data stored on the computer internally.
External Hard Disk Design
An external hard disk drive is designed for portability and flexibility to connect with different computers. The external hard disk contains all the same internal components but is encased in a durable protective enclosure. Here are some key design elements of external hard disks:
- 2.5″ form factor – Most external hard disks use smaller 2.5″ platters and drives designed for portability.
- USB/eSATA/Thunderbolt – External disks connect via USB, eSATA, or Thunderbolt interfaces that provide flexible plug-and-play connectivity.
- Bus-powered – No separate power cord required; external hard disks draw power directly through the interface cable.
- Durable casings – Shock-resistant casings and designs protect the disk from drops and impacts during transport.
- Portable size – Small footprint enables easy portability and storage.
With these features, external hard drives can easily connect to different computers, servers, or devices for flexible data storage and backups.
Internal vs External Storage Capacity
One key difference between internal and external hard disks is storage capacity. Internal hard disks are available in larger capacities since they are not limited by the smaller physical size restrictions of external drives. Some examples:
| Type | Typical Capacities |
|---|---|
| Internal 3.5″ Desktop HDD | 80GB – 16TB |
| External 2.5″ Portable HDD | 120GB – 5TB |
As you can see, internal 3.5″ hard disks can offer multi-terabyte capacities for storing huge amounts of programs and data locally. External drives top out at around 5TB currently for standard single-volume portable drives.
However, external drives offer excellent flexibility and portability. The capacities of external drives are still often large enough for most general data storage, backup, and transfer needs in a portable form factor.
Performance Comparison
In terms of performance, there are some differences between internal vs. external hard drives:
- Transfer speed – External disks are limited by the transfer rate of the interface, such as USB 3.0 or eSATA. Internal SATA hard drives can transfer data faster in most cases.
- Spindle speed – Many external disks use 5400 RPM spindle speeds, while internal disks often use 7200 or 10000 RPM for better performance.
- Seek times – Internal hard disks generally have lower seek times around 8-10 ms, compared to 10-12 ms for many external disks.
- Caching – Larger cache on many internal disks improves read/write speeds.
In real-world terms, a high quality internal 7200 RPM hard drive can transfer data at over 200 MB/s, compared to around 120 MB/s for an average 5400 RPM external hard disk. So while external storage is excellent for overall portability and flexibility, internal disk performance is better for tasks like gaming, video editing, or running application programs.
Reliability Factors
Hard disks contain many delicate mechanical components, so reliability is an important consideration for both internal and external drives. Here are some of the factors:
- Lifespan – Internal hard disks tend to have a shorter lifespan on average, around 3-5 years. External disks can often last 5-10 years due to less constant use.
- Enclosure – The external enclosure protects disks from environmental factors like vibration, shock, temperature changes.
- Components – The same main components like platters and heads will eventually wear out on any hard disk with use over time.
Overall, because external hard disks are often not running constantly like internal system drives, they tend to last a bit longer in terms of lifespan. But internal and external disks still have limited life expectancy and will eventually fail.
Use Cases
Some common use cases where internal vs external hard drives are most ideal:
Internal Hard Disks
- Primary internal storage for desktop and laptop PCs.
- Gaming computers and game consoles where high performance is needed.
- Media centers and home servers for continuously accessed media libraries.
- Workstations that run intensive programs locally and need fast access speed.
External Hard Disks
- Backup storage for personal documents, photos, media files.
- Transferring files between different desktop/laptop computers.
- Expanding limited storage capacity on laptops or games consoles.
- Portable professional photo/video editing storage.
So in summary, internal hard disks are better suited for high-performance local use cases, while external drives provide excellent flexible extra storage and transfer capabilities.
Conclusion
While internal and external hard drives use essentially the same core technologies, there are some important differences in their design, capabilities, performance, and ideal use cases. Key points include:
- External hard disks use smaller form factors and disk sizes for improved portability.
- External drives connect via USB/FireWire/eSATA interfaces for plug-and-play use.
- Internal drives achieve faster transfer speeds and come in larger multi-TB capacities.
- External disks work well for backup/transfer tasks, internal disks for high performance apps.
- Both internal and external hard disks have limited lifespan expectancies.
So in choosing between internal vs. external storage, it depends on your exact needs. If you need maximum capacity, speeds, and 24/7 operation for intensive programs, an internal hard disk is likely the best choice. But for flexible extra capacity that you can bring anywhere, external hard drives are ideal.