This appendix describes the units of measure that are used to express data storage values in the IBM Tape Storage products. For example, in the IBM TS4500 tape library displays data storage values by using decimal (base-10) prefixes and binary (base-2) units of measurement.

Decimal units such as KB, MB, GB, and TB are commonly used to express data storage values, although these values are more accurately expressed by using binary units, such as KiB, MiB, GiB, and TiB. At the kilobyte level, the difference between decimal and binary units of measurement is relatively small (2.4%). This difference grows as data storage values increase, and when values reach terabyte levels, the difference between decimal and binary units approaches 10%.

To reduce the possibility of confusion, this appendix represents data storage by using decimal and binary units. Data storage values are displayed by using the following format:

By this example, the value 512 terabytes is displayed as shown in the following example:

Table A-1 compares the names, symbols, and values of the binary and decimal units.

Table A-2 lists the increasing percentage difference between binary and decimal units.