What version are you using ? 1.2.0 allowed a null bf chance, and I think it returned .1 for LCS and .01 for STS compaction. Have you changed the bf_ chance ? The sstables need to be rebuilt for it to take affect.
> and sstables read is in the skies Not sure what this means. Are you saying it's in a boat on a river, with tangerine trees and marmalade skies ? > SSTable count: 22682 Lots of files there, I imagine this would dilute the effectiveness of the key cache. It's caching (sstable, key) tuples. You may want to look at increasing the sstable_size with LCS. > Compacted row minimum size: 104 > Compacted row maximum size: 263210 > Compacted row mean size: 3041 Take a look at the nodetool cfhistograms to get a better idea of the row size and use that info when consdiering the sstable size. Cheers ----------------- Aaron Morton Freelance Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 26/03/2013, at 6:16 AM, Andras Szerdahelyi <andras.szerdahe...@ignitionone.com> wrote: > 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
