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.