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This has been a problem that we've been battling for some weeks. Whenever large files are copied on the server (both with rsync and cp) the server load initially goes up to 6 or 8 and stabilizes. At some point in the copy load will spike out of control to 50, 100, 150, 200+. At this point we usually fully lose control of the server. This is on a dedicated server with 4GB of RAM and our host keeps telling us that the problem is that MySQL is not getting enough RAM. I don't want to believe that we need more RAM when the server is running fine at normal times.

Any ideas on what is going wrong and how to fix it?

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If MySQL isn't getting enough ram, it usually just dies. That also isn't affected whenever you rsync files.

So you're saying that you have large files (how big?), and you copy them, the load goes up. Have you run iostat ( http://www.cyberciti.biz/tips/linux-disk-performance-monitoring-howto.html ) to see how your machine's I/O performance is doing?

To someone who isn't really all that experienced in performance tuning, it sounds like your CPU is waiting on your I/O to complete, which is backing everything else up. What kind of server is this? Virtual? Dedicated? If it's dedicated, what is the drive configuration? How many spindles?

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+1 for the IO performance. That really sounds like a disk access issue. –  Jeff Snider Jan 25 '10 at 20:34
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