Short History of Data Storage

1725 - 1975: Punch Cards Early data storage was very inefficient Processing of data was very sequential Data was stored as flat files (read from beginning to end) http://royal.pingdom.com/2008/04/08/the-history-of-computer-data-storage-in-pictures/

1932 - Disk Drum - 10kB Formed central memory and secondary storage, also primarily sequential, leading to flat files as best performant data storage. http://royal.pingdom.com/2008/04/08/the-history-of-computer-data-storage-in-pictures/

1951 - Magnetic Tape - 7200 characters / second Tape allowed much greater data densities, but at slower access times. Blocks of data were written to the tape with gaps where the tape is accelerated/decelerated, necessitating more advanced data processing procedures. http://royal.pingdom.com/2008/04/08/the-history-of-computer-data-storage-in-pictures/

1956 - Hard Disk - 5MB Disks allowed for much closer to random access memory than tapes. This allowed the advent of data storage beyond flat files. http://royal.pingdom.com/2008/04/08/the-history-of-computer-data-storage-in-pictures/

http://www.storagesearch.com/chartingtheriseofssds.html / 1982 - Solid State Drive - 2MB SSDs are basically Random Access Memory (RAM) emulating Hard Disks and are optimized for storage instead of access time. http://www.storagesearch.com/chartingtheriseofssds.html /

Data + Base http://ed-thelen.org/SageIntro.html 1960 SAGE anti-aircraft command and control network Cold War Era technology to track and coordinate many separate military installations. http://ed-thelen.org/SageIntro.html

Far more complex than any other computer project of the 1950s The first major system to run in “real-time” – responding immediately to requests from its users and to reports from its sensors. SAGE had to present an up- to-date and consistent representation of the various bombers, fighters and bases to all its users. Popularized the term "data base" to refer to the data underlying the many different views allowed. http://ed-thelen.org/SageIntro.html

Corporate Conceptions of Databases Robert V. Head, "Management Information Systems: A Critical Appraisal", Datamation 13, no. 5 (May 1967):22-27, page 24.

File based storage - 1968 Predecessor of databases Advantages Limitations Various access methods , e.g., sequential, indexed, random Requires extensive programming Separation and isolation: Each program maintains its own set of data Duplication of data – same data is held by different programs, thus, wastes space and resources. High maintenance costs such as ensuing data consistency and controlling access Sharing granularity is very coarse. Weak security. Predecessor of databases

Hierarchical Database - 1968-1980 Advantages Limitations Efficient searching. Complex implementation Less redundant data. Difficult to manage and lack of standards, can’t easily handle many-many relationships. Data independence. Lacks structural independence. Database security and integrity. Files are related in a parent/child manner, with each child file having at most one parent file.

Network Data Model - Early 1960s-1970s Advantages Limitations Ability to handle more relationship types System complexity and difficult to design and maintain Ease of data access Lack of structural independence as data access method is navigational. Data Integrity Data Independence Network data model identified the following three database components: Network schema—database organization[structure] Sub-schema—views of database per user Data management language — at low level, procedural

Relational Databases -1970-Present Advantages Limitations Control of data redundancy, consistency, abstraction, sharing Complexity, size, cost of DBMS Improved data integrity, security, enforcement if standards and economy of scale Higher impact of failure Improved data accessibility and maintenance Instance – a table with rows and columns. Schema – specifies the structure (name of relation, name and type of each column)

Object Oriented Database -1980-Present Advantages Limitations Can efficiently manage a large number of different data types. Switching an existing database to OODBMS requires an entire change from scratch. Objects with complex behaviors are easy to handle using inheritance and polymorphism etc. An OODBMS is typically tied to a specific programming language and an API; this reduces its flexibility. Reduces the large number of relations by creating objects. Ad-hoc queries are difficult to implement as one cannot join two classes as one can join two tables in RDBMS. It supports the modeling and creation of the data as objects.

History of Databases Why was the development of Hard Disks important to databases? Larger Storage Capacity Block Segmentation Low Latency Nice Hum Noise