A single WordPress multisite installation includes several subdomain or subfolder installations like http://domain.com/anothersite/ or http://anothersite.domain.com
- It is easier to backup because all wordpress sites can be found in one MySQL database and under one wordpress folder
- There is only one occurrence of every file in the wordpress installation
- You install a plugin only once. (Nevertheless, you have to set it up several times)
- You need to customize your theme only once and the customization will appear on every installation.
- Some WordPress plugins can’t be installed on WordPress multisite installations
- It looks messy Mysql because it creates multiple occurrences of tables that slightly look the same. If you must perform changes in one installation rather than another, I suggest being aware that in MySQL it may not be easy to identify the right table.
- A plugin code error may crash your whole website.
- If you want to test a plugin, you have to install the plugin on the whole site network.
- The CPU resource is shared between the installations. So if one page is targeted by a DDOS attack, all the installations may suffer from this attack.