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atop:

DSK |   cciss/c0d0 | busy     87% | read 24193e4  | write 4076e4 | KiB/r     26 | KiB/w     77 | MBr/s   7.61 | MBw/s   3.78  | avq     6.07 | avio 2.49 ms |

iostat

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
cciss/c0d0      347.88     15585.01      7748.01 12665004087 6296342774
cciss/c0d0p5    347.22     15584.66      7740.12 12664723850 6289932128

free -m:

             total       used       free     shared    buffers     cached
Mem:          3940       3750        189          0         97       2845
-/+ buffers/cache:        807       3132
Swap:         4094          0       4093

it's a linux box, no dmesg errors with HDD. And I can't find what loads HDD. What I can do here, except changing SATA to SSD :)

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What is the question? How to find what is using the disk? Or something else? –  Jed Daniels Dec 14 '10 at 15:56

4 Answers 4

Assuming your distribution is new enough, take a look at the iotop utility: http://guichaz.free.fr/iotop/.

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well it wasn't hard to install iotop on old centos, but i cant reconfigure kernel (CONFIG_TASK_DELAY_ACCT). So I did atop -d, and it shows that mysql uses 99%. –  nateless Dec 14 '10 at 17:01

Try using lsof to view the open files on your system.

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Well it shows about 4K rows, but how it could helps me to find what loads the HDD? –  nateless Dec 14 '10 at 16:00
    
Look for something out of the ordinary in terms of open files. Is there anything running that shouldn't be? Do a ps, is there anything using up a lot of CPU? –  dmah Dec 14 '10 at 16:04
    
As well, the manpage for atop says that you can press 'd' to get disk statistics. –  dmah Dec 14 '10 at 16:13

Try using "iotop".

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As you mentioned that iotop is showing mysql is contributing to IO load, which I believe is correct. What kind of RAID do you have? Is mysql taking a performance hit?

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