PostgreSQL 12 High Availability Cookbook - Third Edition

How to do it...

Let's begin with a few basic calculations. Look at these following numbers that represent an estimate of interface speed after accounting for network overhead:

• 1,000 Mb/s * B/10 b = 100 MB/s (Megabytes per second)
• 10,000 Mb/s * B/10 b = 1,000 MB/s

Next, consider how many ways this will be distributed. If we have an existing PostgreSQL setup, follow these steps:

1. Execute the following query to determine the number of existing replicas:

SELECT count(*)+1 AS streams 
  FROM pg_stat_replication; 

2. Multiply streams by 160 to find the maximum MB/s needed by replication streams.
3. Execute the following queries together in a psql connection during a busy time of day on a production database:

SELECT SUM(pg_stat_get_db_tuples_fetched(oid)) ...