WordPress multi-site is a built-in function that works within WordPress which allows you to set up a single management install when you have multiple word press sites you want to build. The Multi-site infrastructure will allow you to create multiple WordPress instances that all reside on a single web hosting account.

WordPress multisite, a lot of people are not familiar with this type of WordPress or are new to this technology they may not realize that the company that makes Multisite also provide free WordPress sites for anyone and they actually use the same tool called WordPress Multi-site and they use it to run WordPress.com. They have millions (About 37 million sites) of websites hosted under WP multisite so if someone wants a WP site for free they go to wordpress.com and create new account. Another very popular site that has almost 3 million sites and is using Multisite is Edulogs.org. The WordPress child site would have a url such as joesmith.wordpress.com but if that person decides they want to become more professional and have their own domain name they can register a domain name and go to their WP Multisite account and change it to let’s say: joessmithappliances.com. At that point is not free, WordPress will charge you a small amount of money to host that custom url.  Each month that joesmithappliances.com would be on a Multisite network with literally millions of other websites. WordPress.com will control and limit you to certain things like what you can or cannot install but they manage all the back end and make sure you are up to date and don’t have any outdated plugins or non-secure plugins so you don’t get hacked etc.

Do I need a powerful server to support all these hosted sites?

Absolutely, for a network as large as WordPress.com, you will need a massive infrastructure/hosting platform. But a typical college student’s site that would have about 30 sites WP multisite would work well we a power VPS server or a dedicated server either hosted internally at the school/university or at a hosting company.

Take into consideration that type of server depends on how many sites, pages, users every site has, how big the theme is, how many images there are, are you hosting your own videos, or they are being hosted somewhere else, etc. so many pieces that go together with the sites, it is very hard to say when you need a powerful server.

If someone wants to go out on their own and let’s say start their own hosting company and set up WP multi-site they have to be very careful on how many people or websites they are going to have or people visiting these websites, they have to worry of the bandwidth they support, they should have alot of RAM and there are some other specs to go along with planning to support such a setup. Typical websites right now people are placed on a shared platform. If you expect to support multiple site you can’t expect to do it on a shared platform, you have to spend some money on a real server dedicated or VPS because if these sites take off you need to be able to support the traffic.

Who can use WordPress multi-site

Typically college universities would use it or school districts or clubs that may have multiple locations such as Boys club of America or a College that tend to have multiple departments within the organization anyone that has multiple sites that have a consistent look and feel across all of them. Also companies or organizations that need to segregate control of what people can publish and edit so you use a multi-site to set up those individual sites into word press sites. It's all managed by a webmaster or a super admin that can control what can be installed and what cannot be installed so it protects the organization has a consistent look and feel for the organization.  Helps reduce exposure to rogue plugins or add-ons that may infect other sites and the organization.  At times some user build a website and load a ton of plugins that do all kinds of things.  Even if the plugins don’t infect at this point they can make the website extremely slow.

What are the benefits of using WordPress Multi-site?

The biggest pro I would say with the multisite is that it's a centralized administration tool that allows you to control and provide maintenance and support for multiple sites. Users will be able to login to individual word press sites, but from the super administration panel you can control what versions of the plug-ins or themes are outdated and with a click of a button update them. You can also have a Birdseye view of all the plug-ins installed across all websites you have running. You can also control what the admin for individual word press sites can install so that users can't install outdated, bad or infected plug-ins whether they know they're infected or not. There are times when the organization may need to send out or post content on the website but due to there being multiple sites the super admin can create a single post and then publish it across all child sites on that Multisite network.

What are the drawbacks?

WP has been out for many years: 13-14 years and it is the largest CMS program in the planet. Because of its worldwide usage the type of exposure has attracted tens of thousands of developers that create code, plugins, and add-ons for WordPress. Take into consideration that almost everything you do for WordPress is a plugin, if you want people to sign up for your newsletter that is a plugin, some cost money some are free. As a single WP user you have access to all that, you can search and install any plugin or add-on you want but when you have a multi-site or multiuser WP site a lot of those plugins don’t work, same thing goes for the themes. If you have multisite WP sites and buy a theme for $60.00 you might expect that you can clone one site and add that theme to multiple sites and simply reuse the same theme over and over. What happens is that the companies that make themes or plugins have a way create call backs to check if you have a license for that theme linked to as particular domain. In the situations where they discover your lack of permission they will deactivate the theme if not in other cases they won’t let you install new updates.  You can’t just pay for a plugin like “Gravity Forms” and duplicate it for all your sites so that brings up another issue: How do I get around this issue? Some of these vendors do not provide a multi user license (very few do) so you have to be careful if you jump on a multisite install if you want to get some functionality you will have to pay for multiple licenses or have someone to write custom codes for you. This would be the biggest drawback.

Another drawback would be if you are managing all these sites as the super admin you have the ability to set up backups (this is actually a pro) the con of this is that you now have to setup a backup procedure and figure out a storage facility for all those Multisites or child sites as they call it. Now for every individual site you have to have enough space to back it up, this can really put a lot of pressure on your network when you do the backups. How long does it take to finish backups? This can impact the sites performance, it gets tricky supporting so many sites at once whereas if you have your sites hosted with multiple hosting providers instead of a multi-site you won’t necessarily have this issue so it’s about planning carefully, having a powerful sever to support the sites, an storage where to put the backups and a plan on how to restore them, that’s all.

Would I recommend using WordPress Multisite?

I would recommend multi user site in certain situations, like a college student site. It works best and you can take more advantage of the feature set and the functionality better in an environment like a college university.

I recently used multi-site for a client of mine, University of North Carolina that already had a WP based site but they didn’t want to change that since it was geared towards their town, instead they wanted to create additional websites for each department and everybody segregated to a super admin that controls and maintains the entire environment. The themes are the same, all the sites look the same design wise but the super admin has the control to limit what is being installed in every site.

I wouldn’t use it to set up a hosting provider company. WordPress multisite it is not intended for such an ample and diverse platform such as Hosting companies in which websites can widely vary in design and needs.