Data Compression-for backup and tier 2 storage

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Data Compression

One way to store more with the same is to look at Data Compression and although it is used today mainly for backup and tier 2 storage, its benefits are now being used in compressing data in line for primary storage. This can be of interest particularly where limited space and power are factors.

What is data compression?

Data compression is recombining the bits and bytes that make up your data into a smaller, more compact form. The actual information doesn't change, in case of lossless compression, but the internal representation of it does.

Data compression is a coding/decoding process. The coding side of it uses a particular algorithm to rearrange the internal representation of your data. Generally, an application handles that transparently and in many cases you don't need to know how or why it works. When it's time to actually use the information it has to be decoded, using the reverse process of the method used in the coding process.

Data Compression shrinks down a file so that it takes up less space. This is particularly useful when you have to store large amounts of data. Storage space on disks has a monetary value (disk, Power, Cooling, Rent) and therefore a compressed file which occupies less disk space is could be considered "cheaper" than an uncompressed file. Smaller files are also desirable for data transfer, for example to a disaster recovery site, because the smaller a file the faster it can be transferred. A compressed file appears to increase the speed of data transfer over an uncompressed file.

Types of Data Compression

There are two main types of data compression: lossy and lossless.
 
(1)     Lossy data compression. After lossy data compression is applied the file can never be recovered exactly, as data has been lost. This type of compression does have its uses in sound, video, graphics and picture files. An example of lossy compression would be MP3 format that removes high and low frequencies, which the human ear cannot hear to reduce file size. This compression method is clearly not acceptable for text based files.
 
(2)    Lossless data compression. Lossless data compression works by finding repeated patterns in a message and encoding those patterns in an efficient manner. Lossless data compression is ideal for text.

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