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.