If after several runs, inconsistencies continue to be reported, you may have encountered a corruption. These should be rare, but in the event they occur newer versions of HBase include the hbck tool enabled with automatic repair options.
There are two invariants that when violated create inconsistencies in HBase:
HBase’s region consistency invariant is satisfied if every region is assigned and deployed on exactly one region server, and all places where this state kept is in accordance.
HBase’s table integrity invariant is satisfied if for each table, every possible row key resolves to exactly one region.
Repairs generally work in three phases -- a read-only information gathering phase that identifies
inconsistencies, a table integrity repair phase that restores the table integrity invariant, and then
finally a region consistency repair phase that restores the region consistency invariant.
Starting from version 0.90.0, hbck could detect region consistency problems report on a subset
of possible table integrity problems. It also included the ability to automatically fix the most
common inconsistency, region assignment and deployment consistency problems. This repair
could be done by using the -fix command line option. These problems close regions if they are
open on the wrong server or on multiple region servers and also assigns regions to region
servers if they are not open.
Starting from HBase versions 0.90.7, 0.92.2 and 0.94.0, several new command line options are introduced to aid repairing a corrupted HBase. This hbck sometimes goes by the nickname “uberhbck”. Each particular version of uber hbck is compatible with the HBase’s of the same major version (0.90.7 uberhbck can repair a 0.90.4). However, versions <=0.90.6 and versions <=0.92.1 may require restarting the master or failing over to a backup master.