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i have a server with 512MB RAM running mysql and apache service. I have joomla site inside my server. I want to ask,

  • is there a brief threshold limit of RAM when the server will be stated as busy? like if my server used RAM is 90% can i say that my server is busy? or other percentage threshold?
  • how much load can server with 512MB RAM handle?

i need consideration for server upgrade. thank you.

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closed as not constructive by mdpc, Michael Hampton, David Schwartz, Khaled, dunxd Feb 21 '13 at 11:33

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up vote 0 down vote accepted

Technically speaking, RAM usage going above 90% is not much of a problem. The problem is when you see some real measurable performance problems because of it.

Keep an eye on the swapping stats, if you see too much si and so value in vmstat output combined with a high %sys value in top output, the CPU is spending most of it's time in bringing stuff in and out of disk and memory and that is a thrashing situation. That should be avoided at any cost.

Other than that, if you see most of the RAM is simply in cached state, then ignore it, it is the de facto behavior of linux.

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thanks, it's not all about RAM, i've read that linux tend to use much ram for pagecache. but, what's possibly the cause when i have OOM message that turn off mySQL? do you have idea how much ram allocation mySQL need to handle request normally? – initial05 Feb 21 '13 at 7:27
Show me the OOM messages and I can tell ;) – Soham Chakraborty Feb 21 '13 at 7:38

No, just because memory is used doesn't mean your server is busy. Database servers load the databases into memory to make queries run faster than pulling the data from disk each time.

You can run commands like SHOW STATUS in the database engine to get a better idea of what kind of load is on that moment.

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i have situation where mySQL service on my server is killed when handling requests. it said OOM error. what's possibly the cause? how much ram mySQL normally need? – initial05 Feb 21 '13 at 7:30

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