A Migration to WordPress MU

I’ve been working on one of the largest WordPress MU projects we’ve taken on so far the last couple of days. We’ve been migrating the blogo.nl blogs (a Dutch blog network started in 2005) over to WordPress MU. There were several things in this project that were nice to figure out, I’ll go over two of them, but not before giving a shout out to the guys at WPMU Dev, their support and WP MU plugins have been a huge help.

Migration of the data

We got a bit lucky in this project: the client had his own technical guy, who had written the previous platform himself and was willing to write a WXR exporter, so we could reasonably easily import all the posts through WXR. The issue was that some of these WXR files were about 20 MB large though, and the “normal” upload method of importing WXR’s turned out to be fairly unstable.

Which is why I wrote a new Importer, based on the default WordPress import class:


This new Importer allows you to browse the local filesystem, and pick a WXR file to import:


This new Importer turned out to be a huge blessing in the process of importing 30 something blogs with a total of 29,019 posts and 46,319 comments. I’m not currently planning on releasing this importer, because of the huge amount of support that would take which I simply don’t have time for.

Site wide posts and comments

Another thing that was needed on this site was a global index of all posts and comments. This was when I really found the WPMU Dev Premium package to be worth its money. The Post indexer and Comment Indexer plugins they have are really easy to use, and give you a global table you can easily query on.

Another one of their plugins that’s really cool is the XML Sitemap plugin they offer, which generates an XML sitemap for every single blog. All I had to do was drop in a couple of files into a few directories and add one line to my .htaccess, how cool is that?

James Farmer of WPMU Dev has already agreed to be a guest on the upcoming podcast, so you’ll hear more of these guys soon!

If you have a blog or blog network you’d like to migrate to WordPress MU, check out our WordPress Consulting services!

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10 Responses

  1. rai niaz ahmadBy rai niaz ahmad on 13 July, 2009

    is there any way to migrate wordpress posts into joomla?

    • Joost de ValkBy Joost de Valk on 14 July, 2009

      Now why would you want to do that?

  2. AyalonBy Ayalon on 13 July, 2009

    We had similair problems when migrating from our old CMS to WPMU. With at that time around 70/80 blogs and about 100.000 posts and a multiply in comments. We also made our own import module (from lifetype) which took care of everything, and we wrote many own plugins to deal with the functions of our platform.

    WPMU can be really nice, but you need a lot of custom coding to have everything working correctly if you have a managed platform.

    The MU forums are also great in finding information, but hopefully the integration between “normal” wordpress and MU is done fast, that would make life much easier..

    • Joost de ValkBy Joost de Valk on 14 July, 2009

      Agreed on that, can’t wait for the merge!

  3. AndrewBy Andrew on 14 July, 2009

    Now if you would just write an importer that would move an entire WP or WPMU database to a new domain or a new server without all the extra sql queries I’d be a happy man :)

    It would make life a whole lot easier when testing on localhost is finished and you want to move everything to a live server.

    • figaroBy figaro on 14 July, 2009

      BigDump should do the job nicely.


      • AndrewBy Andrew on 14 July, 2009

        Great tool, but what I’m talking about is a plugin that could take an existing dump and using a form based interface allow you to specify the previous url say http://localhots/wordpress (the testing server) and import it into a live server say http://myliveserver.bogus which would do an update query on all the appropriate url specific data.

        I know it’s only about 3 or 4 queries but how nice would it be to have a plugin to do it on the fly.

        Maybe I could just go to rent a coder and have one made. Could maybe even get some link love out of it.

  4. IainBy Iain on 22 September, 2009

    Hi Yoost, just started using your Google Analytics plugin and loving that – thanks!

    Working now on a plugin that I will install on non-technical clients’ hosting to do a lot of the initial configuration work for me – stuff like WordPress settings, deleting the admin user and adding other users etc.

    One of the things I really wanted to include in the plugin was a way for the client to load a WXR file to give them some starter content on the website, and I don’t know where to start, then I saw this.

    Any chance I could persuade you to send me a copy with ZERO expectation of support on it, in return for a PayPal donation to your good self?


  5. MikeBy Mike on 10 October, 2009

    Can’t you release the importer without support? That would be really sweet :D

  6. DanielBy Daniel on 16 October, 2009

    Hi Joost,

    I’m migrating our blogs to a MU platform. I’m transfering the wp_ tables to their equivalent in wp_x_ MU tables for the new blogs. So far I haven’t found any issue, should I expect one by using this method?