A puzzler for you guys...... all plausible explanations (and suggestions
for proving them) gratefully received.
We run several MySQL database servers in the traditional master-slave
configuration and attempt (rather poorly) to spread select queries
between them. Normally the slave gets 1/3 of the master load. Both
machines have identical configurations, hardware specifications and
network connectivity. The main clients of these databases are PHP
websites without persistent connections. A fail-over pair of machines in
a separate building replicates from the master.
Today (as a result of replication failure) we directed all the traffic
normally sent to the reporting server back to the master server adding a
1/3 to its load. Several areas of the websites got FASTER afterwards and
I'm currenlty at a loss to explain why.