cacti mysql performance

[itkroplis]

I have a 15 log senders ~ 4 log files for each one. IOTOP MySql ~40M/s nonstop.
Performance is very low. Actually does not work.
I stopped new syslog message receipt. But iotop still is ~40M/s
How is possible release syslog queue, without losing the logs in cacti? To normalize performance.