Question-76: Once you delete the data in HBase, when exactly they are physically removed?

Answer: During Major compaction, Because HFiles are immutable, it’s not until a major compaction runs that these tombstone records are reconciled and space is truly recovered from deleted records.

Question-77: Please describe minor compaction?

Answer:

Minor: A minor compaction folds HFiles together, creating a larger HFile from multiple smaller HFiles.

Question-78: Please describe major compactation?

Answer: When a compaction operates over all HFiles in a column family in a given region, it’s called a major compaction. Upon completion of a major compaction, all HFiles in the column family are merged into a single file

Question-79: What is tombstone record?

Answer: The Delete command doesn’t delete the value immediately. Instead, it marks the record for deletion. That is, a new “tombstone” record is written for that value, marking it as deleted. The tombstone is used to indicate that the deleted value should no longer be included in Get or Scan results.

Question-80: Can major compaction manually triggered?

Answer: Major compactions can also be triggered (or a particular region) manually from the shell. This is a relatively expensive operation and isn’t done often. Minor compactions, on the other hand, are relatively lightweight and happen more frequently.