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User:Ruud Koot/Hard disk drive

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Capacity[edit]

PC hard disk drive capacity (in GB) over time. The vertical axis is logarithmic, so the fit line corresponds to exponential growth.

Capacity measurements[edit]

Hard disk manufacturers quote disk capacity in multiples of SI-standard powers of 1000, where a terabyte is 1000 gigabytes and a gigabyte is 1000 megabytes.[1] Many operating systems and utilities – including Microsoft Windows and Apple's MacOS X prior to version 10.6 – report hard disk capacity in powers of 1024, where a terabyte is 1024 gigabytes and a gigabyte is 1024 megabytes. Therefore available space appears less than advertised capacity. The relative difference between the two capacity measurements increases logarithmically with the capacity of the hard disk. The actual number for a formatted capacity will be somewhat smaller still, depending on the file system.

The discrepancy between the two methods of reporting sizes had financial consequences for at least two hard drive manufacturers when a class action suit argued the different methods effectively misled consumers (see Orin Safier v. Western Digital Corporation and Cho v. Seagate Technology (US) Holdings, Inc.).[2][3]

Starting in about 1998, a number of standards and trade organizations approved standards and recommendations for a new set of binary prefixes, proposed earlier by the International Electrotechnical Commission (IEC), that would refer unambiguously to powers of 1024. According to these, the SI prefixes would only be used in the decimal sense, even when referring to data storage capacities. As of 2011 they have seen little adoption in the computer industry. Microsoft Windows continues to reports disk and file sizes using customary binary prefixes, while Apple's MacOS X switched to decimal prefixes in version 10.6,[4] with Ubuntu planning to do so as well.[5]

Advertised, expected, reported and formatted capacities of a 100 MB, 100 GB and 100 TB hard disk drive.
Source Advertised capacity
by manufacturer
Expected capacity
by consumers in class action suit
Reported capacity Formatted capacity
Windows Mac OS X 10.6 NTFS HFS+ ext3
Units Decimal prefixes Bytes Binary prefixes Bytes Difference Binary prefixes Decimal prefixes Decimal prefixes
100 MB 100000000 100 MB 104857600 4.36% 95.37 MB 100 MB (todo)
100 GB 100000000000 100 GB 107374182400 6.87% 93.13 GB
95367.40 MB
100 GB
100 TB 100000000000000 100 TB 109951162777600 9.05% 90.95 TB
93132.30 GB
95367431.64 MB
100 TB

Notes[edit]

  1. ^ i.e. see HGST, Samsung, Seagate, Toshiba and Western Digital websites
  2. ^ http://www.foxnews.com/story/0,2933,201269,00.html Western Digital Settles Hard-Drive Capacity Lawsuit, Associated Press June 28, 2006 retrieved 2010 Nov 25
  3. ^ Seagate lawsuit concludes, settlement announced, bit-tech.net
  4. ^ http://support.apple.com/kb/TS2419
  5. ^ https://wiki.ubuntu.com/UnitsPolicy

References[edit]

  • Mueller, Scott (2011). Upgrading and Repairing PCs (20th ed.). Que. ISBN 978-0789747105.
  • Messmer, Hans-Peter (2001). The Indispensable PC Hardware Book (4th ed.). Addison-Wesley. ISBN 0201596164.