Migrating huge WordPress sites reliably

None of the WordPress migration or backup and restore plugins can handle huge sites reliably – you’ll run into timeout issues etc. Here’s how to migrate your huge sites reliably. The guide below presumes you have an origin WordPress server and a destination WordPress-ready (PHP+MySQL+Nginx) server. Use SSH and Screen
You need to be able to SSH onto your server to do this reliably. You also need to be able to rely on the process completing, even if you switch your computer off or your session gets terminated (like if your network connection drops). Screen is what we need for that purpose – it creates a detachable screen inside SSH that will keep running even when we disconnect from the server.
To use screen, just run:
screen
(then hit enter a few times)
You can then run commands then hit CTRL+A CTRL+D and it will disconnect from the ‘screen’.
You can reattach detached screens using:
screen -r
If there’s more than one detached screen, it’ll instead list the detached screens like this:
And you can reconnect by copying one of the session identifiers into a command like this:
screen -d -r 4674.pts-3.p1
Create a MySQL backup reliably
This technique
Source: https://managewp.org/articles/15204/migrating-huge-wordpress-sites-reliably

source https://williechiu40.wordpress.com/2017/05/26/migrating-huge-wordpress-sites-reliably/