I'm running a single website that barely gets 500 hits a month and I keep getting diskio errors on my wordpress installation. I did some searches and it said to run IOTOP -AO so I did that. I did that and then started scrolling through images on the websites to simulate a single user load (better than nothing, i figure). Any ideas on things to try?

otal DISK READ:       0.00 B/s | Total DISK WRITE:       0.00 B/s
  TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO>    COMMAND
  795 be/4 www-data      4.60 M      8.00 K  0.00 %  0.02 % apache2 -k start
  920 be/3 root          0.00 B    488.00 K  0.00 %  0.02 % [jbd2/xvda-8]
  789 be/4 www-data      4.29 M     20.00 K  0.00 %  0.01 % apache2 -k start
  791 be/4 www-data      4.52 M      8.00 K  0.00 %  0.01 % apache2 -k start
  797 be/4 www-data      4.51 M     24.00 K  0.00 %  0.01 % apache2 -k start
  799 be/4 www-data      4.79 M     16.00 K  0.00 %  0.01 % apache2 -k start
  796 be/4 www-data      4.68 M      8.00 K  0.00 %  0.01 % apache2 -k start
 8995 be/4 mysql       388.00 K     12.00 K  0.00 %  0.01 % mysqld --~-port=3306
  798 be/4 www-data      4.45 M     12.00 K  0.00 %  0.01 % apache2 -k start
 3552 be/4 www-data      4.19 M      4.00 K  0.00 %  0.01 % apache2 -k start
 3404 be/4 mysql         0.00 B      0.00 B  0.00 %  0.00 % mysqld --~-port=3306
15150 be/4 mysql       356.00 K    140.00 K  0.00 %  0.00 % mysqld --~-port=3306
 3420 be/4 mysql         0.00 B   1512.00 K  0.00 %  0.00 % mysqld --~-port=3306
 3418 be/4 mysql         0.00 B     56.00 K  0.00 %  0.00 % mysqld --~-port=3306
28556 be/4 mysql         4.00 K     24.00 K  0.00 %  0.00 % mysqld --~-port=3306
 3409 be/4 mysql         0.00 B      0.00 B  0.00 %  0.00 % mysqld --~-port=3306
 3422 be/4 mysql         8.00 K     24.00 K  0.00 %  0.00 % mysqld --~-port=3306
 3411 be/4 mysql         0.00 B      0.00 B  0.00 %  0.00 % mysqld --~-port=3306
 3412 be/4 mysql         0.00 B      0.00 B  0.00 %  0.00 % mysqld --~-port=3306
 3874 be/4 mysql         0.00 B      8.00 K  0.00 %  0.00 % mysqld --~-port=3306
 3410 be/4 mysql         0.00 B      0.00 B  0.00 %  0.00 % mysqld --~-port=3306
 3799 be/4 root          0.00 B      4.00 K  0.00 %  0.00 % perl /usr~iserv.conf
 2793 be/4 root          0.00 B     60.00 K  0.00 %  0.00 % rsyslogd -c5

If you're not experiencing performance problems, don't worry too much about the disk alert messages. The default setting for this seems to be triggered easily. You might want to keep an eye on things using iotop, but if it doesn't turn up anything then you can raise the notification threshold or disable it.