Handy Estimation Numbers

If not found in your head's L1, L2, L3 cache, memory and local disk, here is a one web page trying to give all the estimation numbers we need!

Data Volume Numbers

Unit Value Number Example
1 Byte (B) 1 2^0 An ASCII Character.
1 KiloByte (KB) 1024 B 2^10 A paragraph of text, an email, 5page paper is 100 KB.
1 MegaByte (MB) 1024 KB 2^20 A high quality picture or a video of 30 seconds are in few MBs.
1 GigaByte (GB) 1024 MB 2^30 My laptop has 512GB and my hard drive too!
1 Terabyte (TB) 1024 GB 2^40 500 hrs worth of movies, RDS one instance can have max 64TB of data.
1 Petabyte (PB) 1024 TB 2^50 1.44 PB of videos are uploaded in Youtube everyday (720,000 hrs) ~ 2022.

Latency Numbers

Time Operation Details
1 ns (nanosecond) L1 cache ref Time to do work by CPU when data is in L1 cache.
5 ns L2 cache ref Time to do work by CPU when data is not in L1 but found in L2 cache.
50 ns L3 cache ref Time to do work by CPU when data is not in L1, L2, but found in L3 cache.
50 ns Mutex Lock/Unlock Mutex locking is this costly!
100 ns Main Memory Ref Time to do work by CPU when data is not in L3 cache, and main memory is reached.
150 us (microsecond) Read 4 KB from SSD Time to read 4KB from a SSD.
250 us Read 1MB seq from Memory 1MB sequential read from Memory.
500 us Round trip in a data center Time taken to go around in a data center and come back.
1 ms (millisecond) Read 1MB seq from SSD 1MB sequential read from SSD.
10 ms Disk Seek Disk Seek
20 ms Read 1MB seq from HDD 1MB sequential read from HDD.
150 ms Send packet from Mum -> Hyd -> Mum Packet transfer and return time across cities

Time Value
1 us (microsecond) 1000 ns (nanosecond)
1 ms (millisecond) 1000 us (microsecond)
1 s (second) 1000 ms (millisecond)

Availability Numbers

Percentage Available How many 9s of Availability? Downtime per day Downtime per month Downtime per year
99% Two 9s 14.4 minutes 72 hours 3.65 days
99.9% Three 9s 1.44 minutes 43.8 minutes 3.65 days
99.99% Four 9s 8.64 seconds 4.38 minutes 52.56 minutes
99.999% Five 9s 864.3 ms 25.9 seconds 5.26 minutes

Round Trip Time By Payload Size and Country

Payload Size Range Round Trips Taken? RTT India (Total) RTT USA (Total)
1 to 13 KB One Round Trip 1200 ms 150 ms
13 KB to 39 KB Two Round Trips 2400 ms 300 ms
39 KB to 91 KB Three Round Trips 3600 ms 450 ms
91 KB to 195 KB Four Round Trips 4800 ms 600 ms

AWS Network Delay

Next time you think how much aws network would add, here are the rough numbers, they depend on factors like instance type, etc.. But this should do:

Across or Same AZ (Availability Zone) Latency (ms)
Across AZ <5ms
Same AZ <1ms

References & Credit