Migration from MS-SQL to PostgreSQL is way of preference or license topic.

For small environment no one will provide tuning of PostgreSQL configuration.

But for bigger backup environment is tuning necessary.

Most of issues is possible to fix with 2 things:

1. exclude PostgreSQL from antivirus
2. change 3 values in postgresql.conf

Excluding from antivirus will prevent to exclude of scanning communication with database.

After migration into PostgreSQL

CPU usage is too high, even with high number of cpu (32 vCPU in this case)

Enterprise Manager is unresponsive (in my case is installed together with VBR)

Jobs are almost not running

Postgresql.conf has 3 basic values for improvement, which need to be increased

max_connections = 100    

shared_buffers = 128MB

work_mem = 4MB

As Veeam is providing connection for each action, it needs to have lot of connection

In my VBR we are backing up 3500 VMs, where 1500 have application aware processing

so I have increased to

max_connections = 3000

shared_buffers = 32GB

work_mem = 128MB

3000 connections × 128 MB = 384,000 MB ≈ 384 GB
384GB + 32GB = 416 GB

So in theory is needed to have on VBR 416 GB of memory

but Veeam does not need so much

Memory is running between 40-70 GB of memory only

CPU is used between 15-45% (32vCPU)

First 8 hours we saw, that Veeam is working on background with new database and console is not so fit.

But after that time, VBR console and Veeam Enterprise Manager is running smoothly.