WordPress MU

I have written a few articles, results of our experience running a WPMU platform with close to 200000 users, describing how to use various caching methods to improve performance, from the specific angle of WPMU. I hope it's not considered spam to post it here, I think it can be helpful for many people.
There should be stuff for the newbies (sql cache, opcode cache) as well as stuff for more advanced users (using APC as object cache with a MU-compatible plugin, tips for implementing WP-Cache even when plugins require dynamicparts included in the page).
Hope it's useful to some of you. I'll be adding more MU-related info in the coming weeks, so check it out from times to times.
Cheers !

Bien et merci. ;)

Am linking to it from my tutorials site.

About as far from spam as you could get, thanks for the brilliant material!

One question though (and, btw, I love the simplicity of just making a list of the 60 most visited blogs!) but have you tested the wp-cache solution http://quentin.unblog.fr/wordpress-mu-wpmu/wpmu-caching/full-page-cache-with-wp-cache-in-wpmu/ with super cache?

And also, was your solution put in place on a cluster with load balancer (and separate db server) or the reverse proxy solution here: http://quentin.unblog.fr/wordpress-mu-wpmu/wpmu-caching/reverse-proxy-cache-and-wpmu/

Thanks again :)

Oh, and can you provide a feed for new content so I can subscribe to it?

And I want my fondue, too. :P

Nice writeup, Q.

I wouldn't mind a feed of it either.

Loving the idea of a list of most visited blogs. :)

Haven't tried wp-super-cache, we had WPCache on before it was out and I don't see a reason to migrate. None of the differences with WP-Cache mentionned on supercache home page make much sense to me. I don't like the idea of plugins messing with my .htaccess, and as I made the argument in my post, you *don't want* the cache enabled for all your users because for 95% of them it will be bad for your perfs. You do want to run a couple of php lines to decide if the current blog is worth using cached pages or not. We have here a list built into an external file included via php, and this list is updated by a cron job. Anytime a blog has more than 20 users online (measured via another plugin we have), the blog is added to the list. In our tests 20 online users is a quite good limit to decide whether a blog should be cached or not. Most often HTTP servers' hard drives have been the bottelnecks in our architecture, so you really don't want to put unnecessary strain on them.

Regarding our architecture, we have a reverse proxy in place for HTTP routing + caching + compression + serving theme files + hosting home page and forums. Reverse proxying is quite convenient when you want to move blogs around on backend HTTP servers, block or redirect temporarily blogs based on URL criteria, etc. We're not redundant at the http level as of yet, mostly because of static files taking a lot of space, and solutions for sharing them across machines being too expensive in terms of cost or performances. We're currently looking into having some servers dedicated to hosting static files, while a cluster of HTTPs would do the PHPing, but that needs quite a bit of hacking to achieve (although the reverse proxy can help too in this domain, by routing /files/ URLs differently than the others). And we need to find servers with huge and fast HDs :-p.

I'll look into providing an rss feed, right now these are pages because my main blog is in french and i didn't want to mix the two languages, but maybe I can play around that using some categories and a tuned home page. I'll look into this.

Regarding the fondue, not so close to christmas and new year, I'm just too full right now :-p.

"you *don't want* the cache enabled for all your users because for 95% of them it will be bad"

Agreed. I had supercaching enabled and for many users, it causes great confusion when they make changes in the backend and don't see them right away. Leads to more support emails. ;-/

As for pages & feeds, I know I saw a plugin for it somewhere...

Fondue? You guys are gonna make me cook it, huh? :P

> Agreed. I had supercaching enabled and for many users,
> it causes great confusion when they make changes in
> the backend and don't see them right away. Leads to
> more support emails. ;-/

Yeah I assumed in my discussion that you configured wp-cache (supercache) in a way that doesn't make this happen. With some well-placed hooks this is easy to achieve, however it does increase the load on disk since anytime a change is made it flushes the cache. However you really don't want to get the support messages like "i changed something and it didn't change". Which is another reason to enable disk caching only in cases where it's worth the trouble.

"Which is another reason to enable disk caching only in cases where it's worth the trouble."

Absolutely.

Also letting the user know that it's been enabled, why it's been enabled, and that they may see a slight delay at times when they make a minor change is a good step too.

After all, how many users are going to complain that their blog is getting better than average attention?

Supercache shouldn't apply to anyone who's logged in... the reason I would usually recommend it is that it works natively with WPMU straight out of the box whereas wp-cache requires a lot of hackin' and alike.

It's also under continuous development... and Donncha's pretty receptive to ideas (i.e. if we can include the 'top blogs list' element) we might even have a crack at getting it into the core!

It's 'chuck another prawn on the barbie' time down here ;)

You're makin' me hungry, Farms. We hit a warm spell (just above freezing) this week, and there's *still* snow on the ground.

I should probably upgrade and tweak my supercache plugin. Just the regular portion of it sometimes causes small issues.