| Whether they are desktop PCs, laptops, servers, or | | | | computer or laptop via USB cable. Some high capacity |
| anything that requires data storage, all data is stored in | | | | models also support firewire. Some external hard |
| a hard drive. There are two types of hard drives, | | | | drives rely on a separate power source (AC adapter) |
| internal and external. | | | | while some smaller capacity models are self-powered |
| According to Usage and Role: | | | | requiring just a data connection. |
| Internal hard drives are always used for storing | | | | According to Transfer Speeds and RPM: |
| system files and primary files necessary to run the | | | | The transfer speeds in internal drives are noticeably |
| system. With their high capacities, they are also used | | | | faster than the one found in external drives. However, |
| for general storage of all file types. | | | | with the advent of USB 3.0 interface and more hard |
| External hard drives serve a backup role where | | | | disks relying on firewire and eSATA connections, |
| important files stored in the internal hard drives are | | | | external hardware is picking up the pace when it |
| copied to the external in case the internal fails or if the | | | | comes to transfer speeds. In terms of RPM (Rotations |
| system unit is lost. It is also used to store files of all | | | | per Minute), internal drives lead the way with the |
| sizes that need to be taken on the go. These drives | | | | common ones having 7200 RPM and the latest ones |
| can be as small as a USB flash drive that can fit in | | | | being as much as 15000 RPM. Many of the external |
| your pocket or can be as large as a standard book. | | | | hard drives today still run on 5200 RPM which means |
| The most important element to know is they are easily | | | | slower read times. |
| portable. | | | | According to Capacity and Cost: |
| According to Connectivity and Location: | | | | Desktop drives generally have increased storage |
| Internal hard drives are found inside the laptop or | | | | capacities at lower costs. However, as the capacities |
| mainframe and usually require them to be screwed in | | | | of these drives increase, the external drives follow the |
| place. The old models make use of a PATA cable to | | | | same pattern leaving them pretty close to each other. |
| connect it directly to the motherboard. The newer | | | | External hard disks are still a bit costly, but prices still |
| models use a thinner SATA cable, which also connect | | | | lower over time. They will remain more expensive than |
| to the motherboard. Both internal models use the same | | | | internal hard disks. |
| power cable to connect to the power supply. | | | | Knowing these differences can greatly help you in |
| Portable hard drives are fully enclosed so they can be | | | | deciding what kind of portable computer memory is |
| placed on a table top in flat or sometimes upright | | | | best for you. |
| positions. Most of the drives today connect to the | | | | |