Data storage values

This topic describes the units of measurement used to express data storage values in the online IBM Spectrum Archive™ Enterprise Edition documentation.

Decimal units (base-10), such as K, MB, GB, and TB, are commonly used to express data storage values. These values, however, are more accurately expressed using binary units (base-2), 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. When values reach terabyte levels, the difference between decimal and binary units approaches 10%.

To avoid confusion, the online Spectrum Archive Enterprise Edition product documentation represents data storage using both decimal and binary units. Data storage values are displayed using the following format:

#### decimal unit (binary unit)

For example, a value of 512 terabytes is displayed:

512 TB (465.6 TiB)

Table 1 compares the names (prefixes), symbols, and values of decimal and binary units. Table 2 shows the increasing percentage of difference between decimal and binary units.

Table 1. Comparison of decimal and binary units and values
Decimal			Binary
Name	Symbol	Value (base-10)	Name	Symbol	Value (base-2)
kilo	K	10³	kibi	Ki	2¹⁰
mega	M	10⁶	mebi	Mi	2²⁰
giga	G	10⁹	gibi	Gi	2³⁰
tera	T	10¹²	tebi	Ti	2⁴⁰
peta	P	10¹⁵	pebi	Pi	2⁵⁰
exa	E	10¹⁸	exbi	Ei	2⁶⁰

Table 2. Percentage difference between decimal and binary units
Decimal value	Binary value	Percentage difference
100 kilobytes (KB)	97.65 kibibytes (KiB)	2.35%
100 megabytes (MB)	95.36 mebibytes (MiB)	4.64%
100 gigabytes (GB)	93.13 gibibytes (GiB)	6.87%
100 terabytes (TB)	90.94 tebibytes (TiB)	9.06%
100 petabytes (PB)	88.81 pebibytes (PiB)	11.19%
100 exabytes (EB)	86.73 exbibytes (EiB)	13.27%