| Operation Type | Approximate Time |
| Time to access local memory | 100 ns |
| SSD disk seek | 100,000 ns |
| Time of a network packet round trip within the same data center | 500,000 ns |
| Disk seek (non-SSD) | 10,000,000 ns |
| Read 1MB sequentially from network | 10,000,000 ns |
| Read 1MB sequentially from disk (non-SSD) | 30,000,000 ns |
| Time of a network packet round trip across Atlantic | 150,000,000 ns |
| How many nanoseconds in a single second | 1,000,000,000 ns |
Table 6-1 Approximate Latencies when Accessing Different Resources
摘自《Web Scalability for Startup Engineers》