Twirrim

One of the fun things with HT is that the second 'core' shares the same L1 cache as the primary. For certain types of tasks that's ideal. For a sizeable number of the things we tend to use servers for, that's quite a negative. If the threads executing on each core aren't directly related and using the same data, it ends up flushing the L1 over and over again, far more quickly than in typical workload.

Alongside what avleen mentions, there are a number of tools from Percona that are essential for anyone dealing with MySQL environments, which you can find in the "Percona Toolkit". For example pt-table-checksum which helps you confirm that data is consistent between servers, and pt-table-sync to help fix it when it isn't.