Anticompaction in Cassandra 2.1

Cassandra 2.1 introduces incremental repairs, which makes repair operations more efficient by not re-repairing already repaired data. Anticompaction is a key concept that enables incremental repairs. It involves splitting an SSTable into two - one containing repaired data and another with unrepaired data. This separation allows for adjustments to compaction strategies, such as size tiered compaction and leveled compaction. The process of migrating to using incremental repairs requires careful handling of SSTables and their levels during the transition period.