Also here is the output from cfhistograms if that helps. Thanks all!
users/cookie_user_lookup histograms
Offset SSTables Write Latency Read Latency Row Size
Column Count
1 574961651 0 0 0
67267
2 50623075 0 0 0
7
3 6977136 0 0 0
866112674
4 1068933 151 0 0
5
5 100458 1752 0 0
0
6 2299 8845 0 0
0
7 25 36376 0 0
0
8 0 118417 1 0
0
10 0 970897 80 0
0
12 0 3154897 706 0
0
14 0 6681561 5633 0
0
17 0 17522902 62716 0
0
20 0 23857810 323821 0
0
24 0 30173547 1756172 0
0
29 0 22315480 7493321 0
0
35 0 9574788 20574499 0
0
42 0 2816872 23382953 15
0
50 0 764169 15332694 16681
0
60 0 245998 10826754 50571
0
72 0 112974 13640480 0
0
86 0 76213 12988932 0
0
103 0 68305 12774730 4
0
124 0 45879 14726045 0
0
149 0 34684 14306264 474654029
0
179 0 24458 8489834 391359834
0
215 0 21349 3616683 98819
0
258 0 12373 1471382 0
0
310 0 8138 2096660 0
0
372 0 6420 12175498 0
0
446 0 4981 44092631 0
0
535 0 4052 19968489 0
0
642 0 3514 30524161 0
0
770 0 3411 88732015 0
0
924 0 3379 36941969 0
0
1109 0 3259 88311470 0
0
1331 0 2925 34015836 0
0
1597 0 2522 25807588 0
0
1916 0 1909 24346980 0
0
2299 0 1083 28822035 0
0
2759 0 646 12627664 0
0
3311 0 489 9374038 0
0
3973 0 331 5114594 0
0
4768 0 797 3119917 0
0
5722 0 317 1805150 0
0
6866 0 94 1105472 0
0
8239 0 68 701533 0
0
9887 0 28 459354 0
0
11864 0 16 304326 0
0
14237 0 20 207982 0
0
17084 0 66 153394 0
0
20501 0 422 134500 0
0
24601 0 716 138258 0
0
29521 0 722 128058 0
0
35425 0 711 123178 0
0
42510 0 663 116942 0
0
51012 0 495 107036 0
0
61214 0 465 109102 0
0
73457 0 370 108586 0
0
88148 0 257 77200 0
0
105778 0 177 47428 0
0
126934 0 59 22524 0
0
152321 0 37 12021 0
0
182785 0 17 7531 0
0
219342 0 28 5127 0
0
263210 0 12 3554 0
0
315852 0 12 2101 0
0
379022 0 4 1417 0
0
454826 0 4 942 0
0
545791 0 1 539 0
0
654949 0 0 341 0
0
785939 0 0 253 0
0
943127 0 0 273 0
0
1131752 0 8 607 0
0
1358102 0 22 2954 0
0
1629722 0 0 493 0
0
1955666 0 0 56 0
0
2346799 0 0 81 0
0
2816159 0 0 13 0
0
3379391 0 0 0 0
0
4055269 0 0 0 0
0
4866323 0 0 0 0
0
5839588 0 0 3 0
0
7007506 0 0 0 0
0
8409007 0 0 0 0
0
10090808 0 0 0 0
0
12108970 0 0 0 0
0
14530764 0 0 0 0
0
17436917 0 0 0 0
0
20924300 0 0 2 0
0
25109160 0 0 1 0
0From: Keith Wright <kwri...@nanigans.com<mailto:kwri...@nanigans.com>> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Date: Friday, July 26, 2013 11:10 PM To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Subject: key cache hit rate and BF false positive Hi all, I am experiencing VERY poor key cache hit rate on my 6 node C* 1.2.4 with Vnode cluster. I am using CQL3 with LCS and yesterday increased my SSTable size from default 5 MB to 256 MB although I did not force a major compaction and am instead letting the new size take effect organically as compactions are normally triggered. The issue for this email is that my key cache hit rate is TERRIBLE at < 1% and my bloom filter false positive rate is around 0.2 (see cfstats , info, and create for example table). I am using the OOTB bloom filter settings and only 300 Mbs of key cache. I'm guessing that I need to increase my bloom_filter_fp_chance from default 0.1 to 0.01 (trigger upgradesstables for it to take effect) and increase my key cache size (my nodes have 32 GB of RAM and I'm running an 8 GB heap on java 7) but I thought I would get everyone's opinion first. My read latency is good but I'm afraid I'll max out the TPS on my SSD drives which are currently hovering around 40% utilization. Should I wait to see what effect the sstable size change has first as it will obviously decrease the number of sstables? What do you recommend for bloom filter and key cache values? I tried upping the key cache size to 600 MB but did not see a sizable difference in hit rate. I am also planning on trying out row cache but wanted to hold off until I got these values handled first. FYI – each node has 3 x 800 GB SSD in JBOD running RF 3. Thanks! Column Family: cookie_user_lookup SSTable count: 13464 SSTables in each level: [1, 3, 101/100, 1022/1000, 10587/10000, 1750] Space used (live): 106151372078 Space used (total): 106870515200 Number of Keys (estimate): 954198528 Memtable Columns Count: 369605 Memtable Data Size: 170078697 Memtable Switch Count: 668 Read Count: 754323272 Read Latency: 1.029 ms. Write Count: 130312827 Write Latency: 0.023 ms. Pending Tasks: 0 Bloom Filter False Positives: 22785986 Bloom Filter False Ratio: 0.24048 Bloom Filter Space Used: 659403424 Compacted row minimum size: 36 Compacted row maximum size: 215 Compacted row mean size: 162 Token : (invoke with -T/--tokens to see all 256 tokens) ID : 6e1a0ac1-6354-40e1-bba4-063c7bb0983d Gossip active : true Thrift active : true Load : 204.64 GB Generation No : 1374259760 Uptime (seconds) : 634791 Heap Memory (MB) : 5601.37 / 8072.00 Data Center : DAL1 Rack : RAC1 Exceptions : 78 Key Cache : size 314572552 (bytes), capacity 314572800 (bytes), 327775491 hits, 3259949221 requests, 0.162 recent hit rate, 14400 save period in seconds Row Cache : size 0 (bytes), capacity 0 (bytes), 0 hits, 0 requests, NaN recent hit rate, 0 save period in seconds CREATE TABLE cookie_user_lookup ( cookie text PRIMARY KEY, creation_time timestamp, opt_out boolean, status int, user_id timeuuid ) WITH bloom_filter_fp_chance=0.100000 AND caching='KEYS_ONLY' AND comment='' AND dclocal_read_repair_chance=0.000000 AND gc_grace_seconds=86400 AND read_repair_chance=0.100000 AND replicate_on_write='true' AND populate_io_cache_on_flush='false' AND compaction={'sstable_size_in_mb': '256', 'class': 'LeveledCompactionStrategy'} AND compression={'chunk_length_kb': '8', 'crc_check_chance': '0.1', 'sstable_compression': 'LZ4Compressor'};
