ms is for microseconds To get a handle on what is happening I would run them both first to reset the recent counts. Then run them and see if they make sense.
Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 4/10/2011, at 9:57 AM, Ramesh Natarajan wrote: > Thanks Aaron. The ms in the latency is it microseconds or milliseconds? > > I ran the 2 commands at the same time. I was expecting the values to be in > the some what similar but from my output earlier , you can see the median in > read latency in histogram output is about 10 milliseconds whereas the cfstats > showed 5 ms. Is this normal? > > thanks > Ramesh > > > On Mon, Oct 3, 2011 at 3:40 PM, aaron morton <aa...@thelastpickle.com> wrote: > Hi Rameash, > > Both tools output the "recent" latency, and while they do this > slightly differently, the result is that it's the latency since the last time > it was checked. Also the two tools use different counters, so using cfstats > will not update cfhistogram. > > > So when you see > > Read Latency: 5.086 ms. > > Write Latency: 0.018 ms. > It means since you last checked the average latency for requests was 5.086 > and 0.018ms > > When you see > > Offset SSTables Write Latency Read Latency Row Size > > Column Count > > 1 4148086 9 198896 0 > > 0 > > it means that 198,896 read requests were completed in 1 *microsecond* and 9 > write requests completed n 1 microsecond. > > Cheers > > > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > > On 4/10/2011, at 4:58 AM, Ramesh Natarajan wrote: > > > 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 > > > >
