We are currently running Xenforo 1.2.3 with MySQL 5.1 and Php 5.3. Pretty old I'd say, so I asked my host to upgrade both. But what shall I ask to install? Php 5.4 or 5.5 and MySQL to 5.5 or 5.6?
Anything else I should keep in mind for this upgrade?
Xf runs great on latest versions of PHP and MySQL. So you can use PHP 5.5 and MySQL 5.6 without worries
I particularly recommend PHP 5.5 because it has a new and very powerful opcode cache.
Ok good to know!
And when this upgrade will take place, do I need to close my forum or can I keep it running? Any idea how long such upgrade could take?
Ok good to know!
And when this upgrade will take place, do I need to close my forum or can I keep it running? Any idea how long such upgrade could take?
You can keep it running.. but I'd close it for the short period of time that you are talking about. Normally the upgrade doesn't take that long. MySQL will be a simple download and shutdown/restart performed by the update process (typically). PHP may be the same, or it could be downloading the source and compiling it (which takes a little longer - depends on the server hardware).
The longest task is to backup the XenForo's database. It's useless 99% of the time but if your MySQL upgrade were to go wrong, you'll be happy to have a backup
Probably is just due to the PHP upgrade itself.
MariaDB or Percona either one are good choices for the mySQL replacement. On my Debian installs I just use Percona... on my CentOS ones I use MariaDB.