PostgreSQL 12 High Availability Cookbook - Third Edition

A working example

Sometimes, these large lists of calculations make more sense if we see them in practice. So let's make the assumption that 2,000 users will use our application each second. This is how this would look:

• 2000 / 50 = 40
• Default queries per page = 10
• Default tables per query = 3
• 40 * 10 * 3 * 2 = 2,400
• 2,400 * 8 = 19,200
• 19,200 IOPS in drives:
• 5" drives: 19,200 / 200 = 96
• 5" drives: 19,200 / 150 = 128
• SSDs: 2 + (19,200 / 50,000) = 2.38 ~ 3
• Add 10%:
• 5" drives: 96 + 9.6 = 105.6 ~ 106
• 5" drives: 128 + 12.8 = 140.8 ~ 141
• SSDs: 3 + 0.3 = 3.3 ~ 4

We are not taking storage capacity into account, which would likely increase our SSD total. We will be discussing capacity soon.