Units of measurement for storage data

IBM® Storage Insights uses decimal and binary units of measurement to express the size of storage data.

Decimal units such as kilobyte (KB), megabyte (MB), and gigabyte (GB) are commonly used to express the size of data. Binary units of measurement include kibibyte (KiB), mebibyte (MiB), and gibibyte (GiB). Table 1 compares the names, symbols, and values of decimal and binary units.
Table 1. Comparison of binary and decimal units and values
Binary Decimal
Name Symbol Value (base 2) Name Symbol Value (base 10)
kibibyte KiB 210 kilobyte KB 103
mebibyte MiB 220 megabyte MB 106
gibibyte GiB 230 gigabyte GB 109
tebibyte TiB 240 terabyte TB 1012
pebibyte PiB 250 petabyte PB 1015
exbibyte EiB 260 exabyte EB 1018

Binary units of measurement express the size of data more accurately. When you compare the size of 100 KB to 100 KiB, the difference is relatively small, 2.35%. However, this difference grows as the size of the data values increases. When you compare the size of 100 TB to 100 TiB, the difference is 9.06%.

In general, IBM Storage Insights Pro uses base 2 values for memory and disk space values, and base 10 values for space on physical hard drives.

Table 2 shows the percentage difference between decimal and binary values across a range of data sizes.
Table 2. Percentage difference between decimal and binary units
Decimal value Binary equivalent of decimal value 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%