Support » Networking WordPress » WordPress multisite memory allocation question.

  • I’m learning about WordPress memory allocation, which oddly seems to be quite important for WordPress functioning correctly but isn’t even mentioned on their systems requirements page. From what I’ve found so far WordPress needs 32MB min and WordPress Multisite needs 64MB min.

    Whatever amount you allocate to WordPress you also have to make sure that PHP has at least that same amount allocated to it. But I’ve got some questions because I’ve talked to tech support at two different hosts now and they are saying things that just don’t seem right to me. I’d like to get some clarification if anyone knows the answers.

    Rackspace tech support said that they have lots of WordPress Multisites running on their servers and he was adamant that they all run just fine on no more than 40MB. Yet WordPress says 64MB and the site I’ve currently got in development (no traffic yet) is using about 45MB just with Catalyst, Gravity and about 15 other plugins, most of them with small memory footprints. Does anyone have experience with WP Multisites and how much memory they actually need once they have multiple sites and traffic?

    The MediaTemple tech support said that if I allocate 64MB to PHP, and there are 5 pages being loaded (page requests) it’s going to use 320MB of memory! That doesn’t even make sense to me unless each of those pages is very inefficient, I can’t believe the amount you allocate is what PHP uses for each page request no matter what is required. If anyone can clarify this for me I’d be grateful. So when you allocate memory to PHP (eg 64MB) are you telling it, use this much (64MB) for each request, or are you saying, collectively all the page requests you can handle at any one time have to use this much (64MB) or less? If it’s the latter, this will sound like a really stupid question, but I’m only asking because this tech guy made it sound like the former is what happens. So I just want to make sure.

    Do all the WordPress operations try to execute in that 64MB that’s been allocated to it? Or is every page request going to be using that much like the tech support suggested would happen for separate PHP scripts.

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  • The MediaTemple tech support said that if I allocate 64MB to PHP, and there are 5 pages being loaded (page requests) it’s going to use 320MB of memory!

    I think the tech means that it’s possible to use 320MB of memory. Which I believe is correct. It’s either per page or per account, and I’m blanking on which.

    Amusingly (to me) my multisite runs fine with 32MB of memory allocated in php.ini, but my SINGLE site needs 64 due to some weird stuff going on. So it’s not a perfect science.

    How many sites are under your multisite?

    Only 8.

    I have another host that has a limit of not more than 256mb memory for longer than 90 seconds.

    Another one has 12 max mysql user connections limit.

    Would a 50 blogs under multisite is ok to the two host limit?

    Just for comparison, I’m running 6,592 sites and php.ini’s memory_limit is set to 128MB

    I would think so, yes, but number of blogs isn’t the same as ‘How much traffic are they getting’ which … really is why my single site needs more than my multi 😉

    @danhgilmore are you using shared hosting platform?

    @ipstenu the blogs are ecommerce sites so lets assume the traffic for each blogs are same as ecommerce sites. What do you think?

    Thank you for your replies.. I appreciate it.

    I think you still can’t know 🙂 Would it be enough for llbean or amazon? No. Would it be enough for Possibly.

    Without knowing how much traffic, it’s all guesswork. I would say it probably will be fine, but you should watch your server load (CPU) and memory consumption regularly.

    IIRC Dan and I are both on VPS.

    As I want to start on shared hosting, generally from the following shared hosting limits that i’ve collected, what would you prefer me to choose for my new/starter multisite? Please help me decide on what host should i pick.

    Webhost #1: 64 mb php memory limit, 25% max of 1Gb and 1 cpu for 30 seconds, 12 mysql users connection.

    Webhost #2: 512mb php memory limit, 25% of the system resources for 90 seconds, no limit on mysql user connections.


    Fair warning – Check to see if they permit multisite on shared hosting. not everyone does. Also make sure that they allow wildcard subdomains if you plan on using them.

    I’d pick #2, mostly b/c of the SQL.

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