Data storage values

TS7700 documentation displays data storage values by using both decimal (base-10) prefixes and binary (base-2) units of measurement.

Decimal units such as K, MB, GB, and TB have commonly been used to express data storage values, though 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, the IBM® TS7700 Information Center represents data storage by using both decimal and binary units. Data storage values are displayed by using the following format:
#### decimal unit (binary unit)
By this example, the value 512 terabytes is displayed as:
512 TB (465.6 TiB)
Table 1 compares the names, symbols, and values of the binary and decimal units. Table 2 shows the increasing percentage of difference between binary and decimal units.
Table 1. Comparison of binary and decimal 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 binary and decimal 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%