I am running a cassandra 0.8.6 cluster. I started a clean test setup and run my tests for a while. Later when I run cfstats and cfhistograms ( both ran at the same time ) the values for Read/Write latency doesn't match. As per cfstats the latency for read and write are 5.086 and 0.018 ms respectively. However per cfhistogram output the latency doesn't look correct. Attached are the output.. Can someone explain how to correlate the data?
Thanks
Ramesh
cfstats
Column Family: uid
SSTable count: 10
Space used (live): 7453864915
Space used (total): 7453864915
Number of Keys (estimate): 2669184
Memtable Columns Count: 6864
Memtable Data Size: 9254197
Memtable Switch Count: 1037
Read Count: 353627031
Read Latency: 5.086 ms.
Write Count: 325803780
Write Latency: 0.018 ms.
Pending Tasks: 0
Key cache capacity: 2000000
Key cache size: 2000000
Key cache hit rate: 0.8106968059650433
Row cache: disabled
Compacted row minimum size: 104
Compacted row maximum size: 11864
Compacted row mean size: 2629
cfhistograms for uid
MSA/uid histograms
Offset SSTables Write Latency Read Latency Row Size
Column Count
1 4148086 9 198896 0
0
2 8680130 2 993805 0
0
3 17138720 2 2487034 0
0
4 29039539 3 4712246 0
0
5 41925392 20 7805708 0
0
6 52669945 126 11641747 0
0
7 57474130 457 15812298 0
0
8 53613212 1034 19846340 0
0
10 67641689 5463 48797478 0
0
12 19456795 15703 52875124 0
0
14 1841556 35196 47573455 0
0
17 3095 102787 51065577 0
0
20 0 145706 27439942 0
0
24 0 196614 14573201 0
0
29 0 237579 4983641 0
0
35 0 489150 2167481 0
0
42 0 1234257 2613908 0
0
50 0 2623421 2887838 0
0
60 0 5991578 1767507 0
0
72 0 13091537 1187687 0
0
86 0 23362939 1001303 0
0
103 0 34216661 966773 0
0
124 0 39232688 580505 3790
3790
149 0 33531717 411380 63631
63631
179 0 28741050 297513 11083
11083
215 0 26604624 211311 82446
82446
258 0 23621426 152905 16650
16650
310 0 21389177 115147 77831
77831
372 0 17854763 89825 77962
77962
446 0 12658366 73162 63647
63647
535 0 8777140 62366 55015
55015
642 0 6714295 58156 89230
89230
770 0 5919024 52929 50298
50298
924 0 5793271 49989 45053
45053
1109 0 5793698 45865 41470
41470
1331 0 5451214 42312 87700
87700
1597 4720406 32027 220189
220189
1916 3745143 27804 313070
313070
2299 2864750 27902 188374
188374
2759 2123842 19042 51096
51096
3311 1560835 17596 4718
4718
3973 1188835 11658 4045
4045
4768 976833 9965 33284
33284
5722 911089 7722 192321
192321
6866 923357 5895 428685
428685
8239 957669 4667 217879
217879
9887 866131 3357 9478
9478
11864 708365 2506 11
11
14237 630587 1847 0
0
17084 557397 1397 0
0
20501 499436 1049 0
0
24601 457665 779 0
0
29521 435142 597 0
0
35425 415220 470 0
0
42510 393854 375 0
0
51012 372677 206 0
0
61214 352421 152 0
0
73457 326874 107 0
0
88148 304298 85 0
0
105778 285494 115 0
0
126934 275249 163 0
0
152321 258549 125 0
0
182785 242338 89 0
0
219342 235146 48 0
0
263210 242166 28 0
0
315852 241692 22 0
0
379022 175100 10 0
0
454826 131247 6 0
0
545791 161308 9 0
0
654949 317944 4 0
0
785939 554445 1 0
0
943127 230545 0 0
0
1131752 63083 0 0
0
1358102 36235 0 0
0
1629722 41269 0 0
0
1955666 10652 0 0
0
2346799 3113 0 0
0
2816159 1016 1 0
0
3379391 148 0 0
0
4055269 18 0 0
0
4866323 9 0 0
0
5839588 0 0 0
0
7007506 0 0 0
0
8409007 0 0 0
0
10090808 0 0 0
0
12108970 0 0 0
0
14530764 0 0 0
0
17436917 0 0 0
0
20924300 0 0 0
0
25109160 0 0 0
0
