You need to free up disk space on your HBase cluster. You delete all versions of your data that is
older than one week. You notice your delete has had minimal impact on your storage availability.
This is because:

A.
You have large store file indexes

B.
HBase has not flushed the MemStore

C.
HBase has not run a minor compaction

D.
HBase has not run a major compaction

Explanation:
The actual deletion of the excess versions is done upon major compaction.
Note: HBase basically never overwrites data but only appends. The data files are rewritten once in
while by a compaction process. A data file is basically a list of key-value pairs, where the key is
the composite {row key, column key, time}. Each time you do a put that writes a new value for an
existing cell, a new key-value pair gets appended to the store. Even if you would specify an
existing timestamp. Doing lots of updates to the same row in a short time span will lead to a lot of
key-value pairs being present in the store. Depending on the garbage collection settings (see
next), these will be removed during the next compaction.