Cassandra

Cassandra

• LSM Tree + SSTable
• PRIMARY KEY(PARTITION KEY, CLUSTERING KEY) Rows are spread across cluster on Partition Key, then ordered by Clustering Key
• Why Cassandra doesn’t need vector clocks
• Delete:
• tombstone
• https://docs.datastax.com/en/cassandra/2.1/cassandra/dml/dml_about_deletes_c.html
• a batch containing conditional updates can only operate within a single partition, because the underlying Paxos implementation only works at partition-level granularity

SSTable

• Cassandra SSTable Storage Format
• The Missing Manual for Leveled Compaction Strategy (Wei Deng & Ryan Svihla, DataStax) | Cassandra Summit 2016
• when to use leveled compaction
• Each level ensures non-overlapping
• SizeTiered is better for write-intensive workloads, and Leveled better for read-intensive

Node repair 2.1

• Frequent data deletions and downed nodes are common causes of data inconsistency. Manual repair: Anti-entropy repair
• Parallel repair will only repair each token range ONCE. if you are using “nodetool repair -pr” you must run it on EVERY node in EVERY data center, no skipping allowed.