I delete data from Cassandra, but disk usage stays the same. What gives?
Data you write to Cassandra gets persisted to SSTables. Since SSTables are immutable, the data can’t actually be removed when you perform a delete, instead, a marker (also called a “tombstone”) is written to indicate the value’s new status. Never fear though, on the first compaction that occurs after GCGraceSeconds (hint: storage-conf.xml) have expired, the data will be expunged completely and the corresponding disk space recovered. See DistributedDeletes for more detail.
