| There are presently two common types of internal | | | | scratches and loss of data. Also, dropping or bumping |
| drives. The more common drive is the hard disk drive, | | | | the hard disk drive can jar the read and write heads to |
| while the solid state drive (SSD) is still making progress. | | | | touch the platter, causing damage to the heads and |
| One the outside there may not appear to be much of | | | | loss of data. For this reason, hard disk drives should |
| a difference between a 2.5" hard drive and an SSD | | | | not be moved while in use, and should be handled |
| with the same form factor. The connection to the | | | | carefully even when not in use. |
| motherboard is the same. The power connectors are | | | | The solid state drive is more expensive, but because it |
| the same. Even the mounting to the computer case or | | | | has no moving parts, it is less fragile. Because data |
| laptop hard drive bay is usually the same. The | | | | access is truly random accesses with virtually no seek |
| difference is in how the drives store and retrieve the | | | | times, it also has much lower performance degradation |
| information. | | | | and is not sensitive to a fragmented file system. |
| Hard disk drives consist of one or more round platters | | | | However, the memory cells in a solid state drive |
| coated with a magnetic substance that can store a | | | | currently can't be written to as often as the magnetic |
| magnetic field. As the platter rotates, a read or write | | | | platters in a hard disk drive. After writing a memory cell |
| head can move over the platter and detect or change | | | | so many times, they wear out. Because of this, special |
| this magnetic field. Solid state drives do not have | | | | technologies may be used to distribute writes across |
| moving parts-hence the name. Instead, a solid state | | | | the disk's memory and to level the wear. |
| drive uses NAND-based flash memory chips. These | | | | While hard disk drives are still more common, solid |
| memory chips, much like USB thumb drives, can retain | | | | state drives are slowly gaining popularity. Commonly |
| their data even when there is no power. Instead of a | | | | found in new laptops, SSDs have no moving devices, |
| moving read or write head, information is stored by | | | | use less power, can take more of a beating, and |
| selecting which memory cell to store information to | | | | provide much faster data access than hard drives in |
| and applying the desired value to that memory cell in | | | | nearly all situations. For example, one of the fastest |
| terms of ones and zeros. | | | | drives right now, the Crucial RealSSD C300, reads |
| The hard drive is still the most common form of | | | | data at up to 355 megabytes per second, which is |
| storage by far in today's computers because they are | | | | more than four times as fast as a regular notebook |
| cheaper - less than $200 for a terabyte when this is | | | | hard drive. On the downside, the capacities are still |
| written. Because the hard disk drive must rotate a | | | | much lower than a similarly priced hard drive and the |
| platter and move a read or write head across the | | | | wear and tear may affect solid state drives slightly |
| platter, there is a slight delay when accessing data. | | | | faster than hard disk drives. As with all new |
| This delay is called the seek time. If a file system | | | | technologies, these teething problems are resolved as |
| becomes severely fragmented, multiple seeks read | | | | they are discovered and there is no doubt that the |
| reading and writing can greatly degrade performance. | | | | SSD will take over the role of the aging hard drive |
| In addition the hard drive can be more easily damaged. | | | | technology-it is only a question of when. For now, they |
| The read and write heads are so close to the platter | | | | are mostly found in high-end, enthusiast computers. |
| that if dust particles get on the platter, they can cause | | | | |