introduction
All Internet resources are data. The programs that store this data do not have to understand what information is contained in the data. Plenty of alternatives exist for storing data safely and accurately and for providing access to that data.
Data can be stored within a computer or somewhere on a network.
what it is
Computer programs store data in the form of gert long strings of ones and zeroes. The computer programs do not need to understand the data to store it. They just have to store it accurately. Data may contain information. If data is presented to someone in a form they understand, such as a wage slip displayed on a computer monitor for an employee, the data gives information to that person. The information given to a person may add to that person's knowledge: the employee may burst into tears when he gains the knowledge that he really should not have spent a whole month's wages on a set of new Carlos Fandango extra-wide wheels for his boy racer car, because he must now eat baked beans on toast until his next wage cheque.
The job of sorting out an organisation's information is called Information Resources Management (IRM). Every organisation has a need for storing these information resources. In the e-commerce world all the computerised information in a business represent business objects. Applications do things with these business objects so applications need access to these business objects.
Copying data from different types of data stores copy data at different speeds. Every computer has a temporary data store which disappears when the power is switched off, such as DIMMs. Most computers also have a permanent store. Permanent storage may be a disk drive, an optical drive such as CD or a DVD drive, or a solid state drive like a flash card or USB pen drive. The problem with permanent storage is that, compared with the temporary storage, transferring data is dog slow. Every computer on the Internet is attached to a network which also contains data stores. Compared to transferring data over a network, permanent storage is greased lightning. Anyone who copies their MP3s from Internet websites using a telephone connection knows what I am talking about.
Data size is measured in a basic unit of computer storage called a byte. Greek and Latin prefixes are used to indicate larger units. Partly because of binary mathematics and partly because it became a standard before anyone sensible managed to stop it, the metric measurement "kilobyte" is actually 1,024 bytes and not 1,000.
| LIC table: equivalent storage measurements | |||
|---|---|---|---|
| Gigabyte (GB) | Megabytes (MB) | Kilobytes (KB) | Bytes |
| 1 | 1,024 | 1,048,576 | 1,073,741,824 |
database server
A centralised data store is also called a data base, as in enemy base and secret underground base. The service which allows access to this data store is called a database server. The WWW is a rambling hypertext database where any object can be linked to anything else. When people talk about a database server they don't mean anything this arty; they are really talking about a more mathematical system called RDBMS (Relational Data Base Management System) which is a specific sort of filing system for data comprised of such things as fields, records, indexes and tables. However, five letter acronyms went out with Pringle sweaters. A database server must allow for existing data to be read, changed and removed and for new data to be written. It must be secure: you don't want just anyone reading wage slips.
a cache
a cache is a private data store. Copies of information are stored in a cache to save time. The varnish application uses a cache. Varnish is a proxy, passing a web client's requests to a web server and passing the replies back. Varnish stores some of the replies in a cache and passes them back when the same questions are asked again. The server does not know anything about these repeat requests. A client sees the web site responding a lot faster.
a buffer
A buffer is a data store that an application makes for its own use. It manages the content itself. A buffer is temporary storage, not permanent. A video stream player uses a buffer to make playback smoother.
what it isn't
Information. Data stores are just lines of ones and zeroes. Data is the basis of information, and information can form knowledge.
where it is
Database servers live in the biz area of the LIC. These supply storage for temporary things like session data. Enterprise data is stored in the enterprise network.
history
In 1801 Joseph-Marie Jacquard stored loom programs on punched cards. The first big computers in the 1940s also used punched cards.
Magnetic memory was invented after the second World War. Magnetic tape appeared in 1951 and magnetic disks in 1956. The floppy disk appeared in 1970. Every few years since a new I/O method for hard disk drives has been flogged to the general public that is less of a snail than the last method, such as SCSI (1982), IDE (1984), SCSI-2 (1994), ATA-2 (1996), ATA-4 (1998) and so on for ever.
The fault tolerant standards called RAID appeared in 1978.
Optical drives kicked off with the CD in 1977. DVD-ROM drives appeared in 1998.
From a network point of view the first few decades of computer history were selfish. There were only mainframe computers that stored everything, with lots of slave consoles connected to them that did not store anything. All mainframe information was stored on the mainframe's disks. For the first few years of personal computer history they too stored their own information on their own disks.
When networks became the must-have fad in the 1980s computers learned to share. Multiple copies of everything were swept away in a distributed service jihad. Applications started to use a centralised information service instead.
