Wednesday, June 15, 2011

Secondary Storage

Disk Cache


A portion of RAM used to speed up access to data on a disk. The RAM can be part of the disk drive itself (sometimes called a hard disk cache or buffer) or it can be general-purpose RAM in the computer that is reserved for use by the disk drive (sometimes called a soft disk cache). Hard disk caches are more effective, but they are also much more expensive, and therefore smaller. Nearly all modern disk drives include a small amount of internal cache.








File Compression



File compression is the practice of packaging a file or files to use less disk space. The File Compression category includes software programs that will archive your files and extract archived files such as ZIP and RAR files. Many products in this category let you manage files and protect them with encryption. Notable titles include WinZip, WinRAR, and 7-Zip.



Internet Hard Drive




The sole purpose of an Internet hard drive is to offer a means of accessing your computer files (pictures, documents, music, videos, etc.) from any computer, as long as that computer has access to the Internet. Similar to depositing money into your bank account, and later withdrawing that same money from any ATM machine, an Internet hard drive will allow you to "deposit" your computer files into a remote hard drive, and then later access those very same files from any other computer.





Optical Disc Drive



In computing, an optical disc drive (ODD) is a disk drive that uses laser light or electromagnetic waves near the light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from discs, but recent drives are commonly both readers and recorders. Recorders are sometimes called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.


File Decompression


Data compression is the encoding of data to consume less space and bandwidth. Data decompression is the reverse--the decoding of compressed data to restore the original data.





Solid- State Drive


A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the same manner of a traditional block i/o hard disk drive. SSDs are distinguished from traditional hard disk drives (HDDs), which are electromechanical devices containing spinning disks and movable read/write heads. SSDs, in contrast, use microchips which retain data in non-volatile memory chipsand contain no moving parts. Compared to electromechanical HDDs, SSDs are typically less susceptible to physical shock, are silent, and have lower access time and latency, but are more expensive per gigabyte (GB) and typically support a limited number of writes over the life of the device. SSDs use the same interface as hard disk drives, thus easily replacing them in most applications.


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