系统内冗余或重复数据的度量，表明存储和潜在性能问题效率低下。
1 UD = 0.5 PB
1 PB = 2 UD
例子:
将15 有用的数据转换为奇偶校验的冗余：
15 UD = 7.5 PB
| 有用的数据 | 奇偶校验的冗余 |
|---|---|
| 0.01 UD | 0.005 PB |
| 0.1 UD | 0.05 PB |
| 1 UD | 0.5 PB |
| 2 UD | 1 PB |
| 3 UD | 1.5 PB |
| 5 UD | 2.5 PB |
| 10 UD | 5 PB |
| 20 UD | 10 PB |
| 30 UD | 15 PB |
| 40 UD | 20 PB |
| 50 UD | 25 PB |
| 60 UD | 30 PB |
| 70 UD | 35 PB |
| 80 UD | 40 PB |
| 90 UD | 45 PB |
| 100 UD | 50 PB |
| 250 UD | 125 PB |
| 500 UD | 250 PB |
| 750 UD | 375 PB |
| 1000 UD | 500 PB |
| 10000 UD | 5,000 PB |
| 100000 UD | 50,000 PB |
规则