Linux – high iostat load on linux

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 🙂