My current website is running on the oldstable Debian 6 and Redmine 1.0.x while the recent stable version of Debian is 7 and the latest version of Redmine is 2.4.x! But such old versions are not the problem – the problem is that they do not allow me to run new plugins and features. Also the official support of Debian 6 is to be stopped soon and this means no more security updates for the OS!
Due to peculiar circumstances the upgrade also implies the change of server and, therefore, IP address. So, it’s going to take some time, as it requires data transfer between old and new server.