One common misconception that we don’t quite understand, but comes up often when we are contacted about possibly doing upgrades of software on websites, is a belief that after an upgrade the content of the website will not be there anymore and need to be transferred back to it. We are not sure where that would come from, since if that would be the case there wouldn’t be a reason for doing upgrades, since you could cut out a step and just do a new install of the software and do a transfer, if that was the case. (If an “upgrade” required that, it would actually be a migration, not an upgrade.)
Because it specifically came up recently, we wanted to make it clear to a wider audience that upgrading Moodle will not cause courses or other content to go missing and need to be restored. That being said when we do upgrades of Moodle we first do a test of the upgrade to insure that nothing goes wrong during the upgrade process and everything will work with the new version of Moodle, since a real concern is that there might be an incompatibility between the new version of Moodle and, say, the hosting environment the website is hosted on.