Considerations for splitting tables
You can split tables during table creation based on the target number of regions per RegionServer to avoid costly dynamic splitting as the table starts to fill.
Splitting table ensures that the regions in the pre-split table are distributed across many host machines. Pre-splitting a table avoids the cost of compactions required to rewrite the data into separate physical files during automatic splitting.
If a table is expected to grow very large, you should create at least one region per RegionServer. However, you should not immediately split the table into the total number of desired regions. Rather, choose a low to intermediate value. For multiple tables, you should not create more than one region per RegionServer, especially if you are uncertain how large the table will grow. Creating too many regions for a table that will never exceed 100 MB is not useful; a single region can adequately service a table of this size.