By default in HBase, each region is served by a single region server. Writes and reads always go to that regionserver, and are consistent across a single row (HBase is a CP system). In this mode, when a regionserver goes offline its regions are (eventually) reassigned to a different region server. During this process the region is unavailable, but there's no loss of consistency.
Hbase 0.98 (I think?) introduced a feature called "timeline consistency" that allows reads from replica regionservers. This has to be enabled for a table and has to be specified on the query side. If it is, you have the option of falling back to the replica if the primary doesn't respond within a deadline. This may be a good tradeoff if you value availability over consistency.
Hbase 0.98 (I think?) introduced a feature called "timeline consistency" that allows reads from replica regionservers. This has to be enabled for a table and has to be specified on the query side. If it is, you have the option of falling back to the replica if the primary doesn't respond within a deadline. This may be a good tradeoff if you value availability over consistency.