A table’s data is stored in regions. A single table’s data can be stored in one or more regions. A region is a sorted set consisting of a range of adjacent rows stored together. A table’s data can be stored in one or more regions depending on how many rows are stored in a region. RegionServers manage data stored in regions. When HBase starts, the Master assigns regions to RegionServers. If required for load balancing, the Master also reassigns regions across the RegionServers. As discussed in Chapter 9, when the number of row keys in a region becomes too large, the region splits into approximately two equal halves, and this is called auto-sharding. Regions split automatically or manually with growing data as a region becomes too large. A RegionServer does not compact and splits in parallel. For example, a table’s row keys are not stored in the same region; a table's row keys are distributed across the cluster stored on different regions on different RegionServers.