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WordPress Max File Size Reached? Check WPMU Limits.

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I ran into yet another WordPress detour today while posting a quick email on my other blog.   While uploading a small PNG file, about 200kb in size, I received a “Maximum File Limit Reached, the maximum upload size is 80KB”.  However this message was different.  It was not formatted the same way as other file upload limits I’ve hit before.    Maybe it was the WordPress 3.7.1 patch?    I investigated the normal culprits, searching /etc/php.ini on my server and checking the “basic” settings including:

upload_max_filesize
post_max_size

Both settings were WAY above 80KB.

I looked into the WordPress configuration files.  Maybe a new limit had been put in place.    Nothing.

This is a site that is part of a multisite (WPMU) installation of WordPress.   Maybe the limit was in the database.    Search the wp_options table even inside of serialized options.  No 80KB limits to be found.

Then I had an idea.   WPMU DOES have a “maximum total uploads” setting.    Could that possibly mean “maximum total file space for ALL sites combined”?    It is set to 500MB “out of the box”, which seems rather limited give even most shared hosting sites now offer multi-GB hosting.     I tweaked it to read 512MB.    Sure enough my file uploaded without a problem.      Turns out the collective upload file store on the sites on the server are sharing this limit.    Since I have 20GB available I think I’ll set this to a much higher number.    I can see why it exists, but maybe a future version of WordPress can give a bit more information than “upload limit reached”… maybe a little hint like “The WPMU upload storage limit has been reached, there is only enough space allowed for 80KB more stuff.”.

Maybe this post will help some other WPMU site admin from spinning their wheels for an hour trying to figure out what is going on.