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MySQL transactions per second vs. fsyncs per second (2020)
Just wondering how many transactions or writes per second MySQL can handle? While it depends on many factors, fundamentally, about as many transactions as MySQL can commit to disk per second. A modern disk can do ~1000 fsyncs per second, but MySQL will group multiple writes with each fsync.
When we consult the reference napkin numbers, we see that the fsync(2) in step (2) is by far the slowest operation in the blocking chain at 1 ms. This doesn’t guarantee the actual bits are committed on disk, which means an unexpected loss of power would erase the data, dropping our ACID-compliance on the floor. Because the WAL is touched twice as part of the 2-factor commit, it explains why we see roughly ~2x the number of fsync to that over the bin-log from the bpftrace output above.
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