Latency timings with computers and Information Technology.
Lots of thanks to Jeff Dean for doing the math.
Area | Nanoseconds |
L1 cache reference | 0.5 |
Branch mispredict | 5 |
L2 cache reference | 7 |
Mutex lock/unlock | 100 |
Main memory reference | 100 |
Compress 1K bytes with Zippy | 10,000 |
SSD Random Read | 16,000 |
Send 2K bytes over 1 Gbps network | 20,000 |
Read 1,000,000 bytes sequentially from SSD | 49,000 |
Read 1 MB sequentially from memory | 250,000 |
Round trip within same datacenter | 500,000 |
Read 1 MB sequentially from disk | 825,000 |
Disk seek (15k drive) | 2,000,000 |
Read 1 MB sequentially from network | 10,000,000 |
Send packet CA→Netherlands→CA | 150,000,000 |
It's amazing how slow networks and disk(s) are compared to the CPU!
Info | HD | Speed |
Rotational Latency | 7200RPM HDD | 1 rotation per 8.33 milliseconds. Best case: 0, worst: 8.33ms |
Seek time | 7200RPM HDD | The worst case seek time is around 8ms on a typical hard drive, for an average of 4ms. |
IO Size | 7200RPM HDD | 1MB → 2MB depending on where on platter it is. |