NDB Connections per Disk?
I do not understand what this setting does.
To tailor the backup process to your specific needs and infrastructure, you can adjust the number of NBD connections per exported disk. This setting is accessible in the Advanced backup job section and allows for further customization to optimize performance according to your network conditions and backup requirements:
More connections = faster backup? What's the trade-off?
More connections = more speed since we doing things in parallel. But your mileage may vary, so you can start at 2, then 4 then 8 etc.
Eg in our infrastructure, 4 is a good sweetspot.
I second 4 being a good sweet spot, I personally have seen very little improvement from going higher than 4 in my environments.