Hello list, Could anyone shed some light on how an FP chance of 0.01 coexist with a measured FP ratio of .. 0.98 ? Am I reading this wrong or are 98% of the requests hitting the bloom filter create a false positive while the "target" false ratio is 0.01? ( Also key cache hit ratio is around 0.001 and sstables read is in the skies ( non-exponential (non-) drop off for LCS ) but that should be filed under "effect" and not "cause"? )
[default@unknown] use KS; Authenticated to keyspace: KS [default@KS] describe CF; ColumnFamily: CF Key Validation Class: org.apache.cassandra.db.marshal.BytesType Default column value validator: org.apache.cassandra.db.marshal.BytesType Columns sorted by: org.apache.cassandra.db.marshal.BytesType GC grace seconds: 691200 Compaction min/max thresholds: 4/32 Read repair chance: 0.1 DC Local Read repair chance: 0.0 Replicate on write: true Caching: ALL Bloom Filter FP chance: 0.01 Built indexes: [] Compaction Strategy: org.apache.cassandra.db.compaction.LeveledCompactionStrategy Compaction Strategy Options: sstable_size_in_mb: 5 Compression Options: sstable_compression: org.apache.cassandra.io.compress.SnappyCompressor Keyspace: KS Read Count: 628950 Read Latency: 93.19921121869784 ms. Write Count: 1219021 Write Latency: 0.14352380885973254 ms. Pending Tasks: 0 Column Family: CF SSTable count: 22682 Space used (live): 119771434915 Space used (total): 119771434915 Number of Keys (estimate): 203837952 Memtable Columns Count: 13125 Memtable Data Size: 33212827 Memtable Switch Count: 15 Read Count: 629009 Read Latency: 88.434 ms. Write Count: 1219038 Write Latency: 0.095 ms. Pending Tasks: 0 Bloom Filter False Positives: 37939419 Bloom Filter False Ratio: 0.97928 Bloom Filter Space Used: 261572784 Compacted row minimum size: 104 Compacted row maximum size: 263210 Compacted row mean size: 3041 I upgraded sstables after changing the FP chance Thanks! Andras