Multi-DB plugin & WP-Engine hosting


I just moved my wordpress multisite network to WP-Engine hosting, and I had some questions about the Multi-DB plugin.

1) Do I really need Multi-DB if i'm using WPengine?

2) Is there a way to backup all the Multi-Databases?

3) How big should the database file size be to consider installing the multi-db plugin?

4) If I wanted to undo the multi-db plugin install, can I do that?


  • Vaughan


    it's not so much the size of the db, more of how many subsites you are using on the network. you will not see any benefit with just a few hundred sites, but if you are expecting thousands of subsites, then it will benefit you. as far as wpengine is concerned, wpengine has it's own load balancing i think, so i don't think multi-db would be necessary.

    i do not think you'd be able to uninstall it after very easily. i don't know enough about it to be able to advise you properly on that, so i will ask the developer for some feedback on this for you.

    hope this helps

  • webatonic1

    I am expecting tens of thousands of sites in my multisite network. WP-Engine is currently hosting my installation and they are telling me that on their servers they don't have any client with more than a thousand sites in their network, in fact they continue to explain to me that once I reach a few hundred sites the database will become too big and the whole network will experience slow loading time.

    I asked if they support Multi-DB and they DO NOT! They DO support HyperDB in their premium accounts.

    Should I use Multi-DB or HypeDB to scale my multisite network to tens of thousands of sites?

  • Eugene Manuilov

    Hi @webatonic1

    There is a difference between Multi-Db and HyperDb plugins. Multi-Db allows you to build and use horizontal shard which allows you reduce workload on your database.

    Should I use Multi-DB or HypeDB to scale my multisite network to tens of thousands of sites?

    I would say - yes, you should. But pay attention that Multi-Db plugin adds some restrictions for else plugins and not all plugins are compatible with horizontal shard. So if you want to use Multi-Db, then you need be confident that all plugins will work properly.


  • Eugene Manuilov

    Also I would like to warn you about possible issue regarding to Multi-Db plugin. As I said above the Multi-Db plugin allows you to create a horizontal shard of databases. It will increase performance of your network. But the issue is that not all 3rd party plugins are optimized to work with horizontal shard, even more, some of them could fail, because written without horizontal sharding support.

    So you need to monitor your debug.log for any kind of WordPress database error. If you find any db error, then show it to me and I will look at it.

    P.S.: don't read this message as "all plugins will fail 100%", it is not true, the most part of them will work, but there is a chance that few of them won't. Just keep your hand on a pulse and all will be fine.


  • webatonic1

    so Multi-DB is horizontal scaling, and adding additional servers with CPU and Storage is vertical scaling.

    1) If that is the case then when using Multi-DB to partition the main database into 4096 databases and having 100,000 child sites evenly spread across these tables can save money on buying more CPU & Memory/server resources?

    2) At what point do I need to assign a dedicated server for these partitioned databases?

  • Eugene Manuilov

    At what point do I need to assign a dedicated server for these partitioned databases?

    It's a hard question, because there is no "silver bullet" to cover all cases. The answer on this question is always unique for unique case, but in general you need to monitor your server workload and when you see that your server can't handle an amount of requests, then you need to consider more powerful environment.

    To be honest I am not very good at server side administration and can't give you comprehensive answer. You need to ask an admin guy, who understands it better.

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