One of the things we find ourselves doing more and more of at Reclaim Hosting is managed hosting, in particular for WordPress Multisite (WPMS). In the end was the beginning for this blog. So, I was on a call last week were the discussion around running multiple, independent WPMS instances versus one WPMS instance with multiple networks, i.e. sites.stateu.org and courses.stateu.org represent two functioning WPMS instances using subdomains (or subdirectories) such as mysite.sites.stateu.org or mycourse.courses.stateu.org that both point and share one set of core WordPress files. I experimented with this over 10 years ago by running a WPMS (then called WPMU) service for Longwood University off the core WordPress files of UMW Blogs. I thought it would be revolutionary for the ability to share infrastructure across Virginia public institutions of higher ed, but not so much. That said, I was glad to see Curtiss Grymala to take the whole idea of multi-networks to the next level for UMW’s main website.
Anyway, enough about the past, that was then, this is now …. for now. The question is why would you run several independent WPMS instances with distinct core files versus running multiple instances of WPMS off of one shared set of files, plugins, themes, etc.? For me the value of running everything off one shared set of files was shared themes, plugins, and updates that make management easier than across numerous separate installs.* Another benefit was a single space for site/user administration between networks. Additionally, managing single sign-on through one instance should prove a bit easier for setup, but will need to double-check on this one. I also know you can have various portals for each WPMS network mapped on a single set of files, so it will not be confusing for the users, for them the fact they share core files will be invisible. So, in this regard the choice comes down to whether or not consolidation makes sense for the WPMS admin, which is often a question of convenience.
But there may be some practical reasons not to use a multi-network setup. Like, for example, if you are planing on running thousands of sites on each of these WPMS instances you may want to keep them separate given scaling issue with the WPMS database.** Having three WPMS instances share core files means if one goes down, they all go down, which can be an issue. Also, if you have an existing WPMS site you want to incorporate into an existing multi-network setup it may get tricky depending on whether there are shared users across the various instances of WPMS that you’re combining. I will have to do more research here, and would love to know about anyone’s experience in this regard, but I imagine users across a multi-network instance would need to be able to access the various networks with the same email/username across networks for the sake of both convenience and single sign-on (which are often one in the same).
Which raises another question that I’m unsure of, if users sign-in through one network of a multi-network setup can they cleanly move between sites on different networks? I’m wondering if keeping single sign-on and users separate in this instance may prove less problematic in the long run. I’ll be working through these scenarios this week, but wanted to post this here cause I know a few folks have experience with running multi-networks on bit sites and wanted to be sure I was not overlooking any major red flags before making some recommendations.
*It also allows you to share any premium themes or plugins across one instance.
**Although if this is the case you will have to shard databases anyway, so one could argue it would be easier to do that for one instance rather than many.