If the locks set on the index records in that range do not lock out inserts made in the gaps, another session can insert a new row into the table.
Consequently, if you were to execute the same In this case, table has no indexes, so searches and index scans use the hidden clustered index for record locking (see Section 14.11.9, “Clustered and Secondary Indexes”).
NOTE: The time to Initialise the innodb buffer pool is roughly proportional to the size of the pool created.
On large installations[*] this initialisation time may be significant.[*] 2009/10 Initialising a 10 GB buffer pool takes 6 seconds, larger configurations may take proportionally longer.
How each settings affects performance depends on hardware configuration and workload.
Benchmark your particular configuration to decide which setting to use, or whether to keep the default setting. The mix of read and write operations in your workload can affect how a setting performs.
For general I/O tuning advice, see Section 8.5.7, “Optimizing Inno DB Disk I/O”.Prior to My SQL 5.1.24, the default is greater than 100.