Units of measurement for storage data
IBM Spectrum Control 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.
| 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 Spectrum Control 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.
| 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% |