Data Caching & Speed of Communication

An interesting comparison of speed of computer storage:

Teach Yourself Programming in Ten Years by Peter Norvig (AI, Stanford, Google)
On his classes Peter suggests importance of being aware and estimating order of magnitude
of processing time of algorithms, and adjusting programs accordingly, avoid "premature optimizations". For that a higher abstraction language like Python is proffered.

"Approximate timing for various operations on a typical PC:"

execute typical instruction	1/1,000,000,000 sec = 1 nanosec
fetch from L1 cache memory	0.5 nanosec
branch misprediction	5 nanosec
fetch from L2 cache memory	7 nanosec
Mutex lock/unlock	25 nanosec
fetch from main memory	100 nanosec
send 2K bytes over 1Gbps network	20,000 nanosec
read 1MB sequentially from memory	250,000 nanosec
fetch from new disk location (seek)	8,000,000 nanosec
read 1MB sequentially from disk	20,000,000 nanosec
send packet US to Europe and back	150 milliseconds = 150,000,000 nanosec

Coding Blocks podcast Episode 45 – Caching Overview and Hardware
"In more relatable terms.

• 1 second for L1 Cache  (actual is 0.5 ns)
• 5 days for memory
• 11 days for data center
• 23 days for SSD
• 15 months for HD
• Almost 10 years for internet! (actual is 150 ms)"

Latency Numbers Every Programmer Should Know · GitHub

Visual Animation:
Relative Memory Access speeds (Lesson 3)