Your client application calls the following method for all puts to the single table notifications:
‘put.setWriteToWAL, (false);
One region, region1, for the notifications table is assigned to RegionServer rs1. Which of the
following statements describes the result of RegionServer rs1 crashing?

A.
All data in the notifications table is lost

B.
No data is lost

C.
All data for all tables not flushed to disk on RegionServer rs1 is lost

D.
Data for your client application in the MemStores for region1 is lost

Explanation:
What role does ‘setWriteToWAL(false)’ play?
HBase uses a write ahead log, if you don’t write to it you will lose
all the data that’s only in the memstores when a region server fails.
This setting is useful for importing a lot of data.