Recently my Debian Linux server has been experiencing slow web server response times. I've investigated and it seems that MySQL is the culprit, yet there are no slow queries indicated by the slow queries log and when I check SHOW FULL PROCESSLIST I have to be quick to see any queries that are actually running (due to the fact that they finish so quickly).
I've noticed that disk I/O speeds are significantly reduced when MySQL goes on these sprees of being slow. According to hdparm:
Timing cached reads: 8012 MB in 2.00 seconds = 4009.64 MB/sec Timing buffered disk reads: 2 MB in 3.29 seconds = 623.18 kB/sec
When MySQL is disabled, buffered disk reads rise to about 120 MB/sec.
The bottom line is, what could be causing the heavy impact to general I/O speeds of other processes on the server? Does MySQL need some sort of optimization?
Thanks in advance for any suggestions.