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Our site goes down because the IO on our database servers is too slow.

Troubleshooting this we found that mysql is really really slow. It's constantly reading from disk and I think not using enough memory. It's using about 30G when it usually uses about 100G.

Here is the pt-mysql-summary https://gist.github.com/simao/4e809db0aa3a588764e2

What can I check to see what is causing massive IO reads from mysql?

How can I find out why mysql is so slow and using so much disk IO?

Thank you

Update:

This is the current iostat https://gist.github.com/simao/3657e6ac9fab0376acc0

But we are up at the moment and when we are down IO is 100% and disk reads are really slow.

We are using InnoDB with SSD storage on a dedicated machine.

  • iostat command on linux would give you better idea about os level I/O operations..more disabled direct i/o kernel level parameter could also cause high i/o..please mention storage being used currently in your environment..? – Nawaz Sohail Jan 9 '15 at 8:29
  • You may need to disable sync_binlog as it may be causing high i/o..Use Query cache and disable query long parameter and see it helps – Nawaz Sohail Jan 9 '15 at 8:34

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