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I run a linode VPS with 512MB of memory and I was wondering if a PHP accelerator or PHp cache is a must have?

The point of the server is a vBulletin forum.

Which one would you recommend if so?

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up vote 3 down vote accepted

protip: 99% of systems administration is trial & error

no one can tell you what the memory-footprint/performance tradeoff for your version of vbulletin running your inevitable customizations at your traffic levels, sharing a tiny vps with whatever else you're doing, is going to be.

that said, apc is pretty much standard-issue at this point. I'd have to have a reason not to set it up on any new php environment, and you haven't shown one yet.

edit: and if this is apache/mod_php you'd better have your maxclients/serverlimit down at like 10

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Thanks for the tips. I actually have it at 24 right now but I do notice apache gobbling up memory sometimes. Do you say 10 because of the memory? If I upgrade to 728 what would you bump it to from your experience? I understand it's trial and error and I'm learning a lot but advice is always a helpful guide. – Daniel Fischer Feb 15 '10 at 4:29
mpm_prefork_module: StartServers 1 MinSpareServers 3 MaxSpareServers 6 ServerLimit 24 MaxClients 24 MaxRequestsPerChild 3000 – Daniel Fischer Feb 15 '10 at 4:29
Is the default configuration sufficient for APC? – Daniel Fischer Feb 15 '10 at 4:58
Yes, always leave things at the default until you can prove a difference is worth it with a test. In your case I'd focus on gathering facts first, make decisions later. Something like Munin will give you nice charts and is very quick and easy to setup. – cagenut Feb 15 '10 at 13:03
Thanks. I did some research and I hear to choose collectd over munin. What would you say to that? – Daniel Fischer Feb 15 '10 at 19:01

The best way to try this is doing some tests and testing the performance.

I used Accelerators sometime ago when I deployed SquirrelMail to 100k users, the performance increased 5 times. After that I got other problems and solved using a reverse proxy in the front and distributing the load through more machines.

But it's a great solution and the unique thing you can do is test.

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