Or maybe the clients always connect to that server which can satisfy all reads. They have 3 nodes with RF=3.
-Bryan On Wed, Dec 19, 2012 at 12:15 PM, aaron morton <aa...@thelastpickle.com>wrote: > Is there a sustained difference or did it settle back ? > Could this have been compaction or repair or upgrade tables working ? > > Do the read / write counts available in nodetool cfstats show anything > different ? > > Cheers > ----------------- > Aaron Morton > Freelance Cassandra Developer > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 19/12/2012, at 6:26 AM, Alain RODRIGUEZ <arodr...@gmail.com> wrote: > > Hi, > > I am experimenting a strange issue in my C* 1.1.6, 3 node, RF=3 cluster. > > root@ip-10-64-177-38:~# nodetool ring > Note: Ownership information does not include topology, please specify a > keyspace. > Address DC Rack Status State Load > Owns Token > > 141784319550391032739561396922763706368 > 10.64.167.32 eu-west 1b Up Normal 178.37 GB > 33.33% 28356863910078203714492389662765613056 > 10.250.202.154 eu-west 1b Up Normal 174.93 GB > 33.33% 85070591730234615865843651857942052863 > 10.64.177.38 eu-west 1b Up Normal 167.13 GB > 33.33% 141784319550391032739561396922763706368 > > root@ip-10-64-177-38:~# nodetool ring cassa_teads > Address DC Rack Status State Load > Effective-Ownership Token > > 141784319550391032739561396922763706368 > 10.64.167.32 eu-west 1b Up Normal 178.37 GB > 100.00% 28356863910078203714492389662765613056 > 10.250.202.154 eu-west 1b Up Normal 174.93 GB > 100.00% 85070591730234615865843651857942052863 > 10.64.177.38 eu-west 1b Up Normal 167.13 GB > 100.00% 141784319550391032739561396922763706368 > > My cluster is well balanced, all the nodes have an identical > configuration, but yet I have a lot of disk reads on one of them as you can > see in these screenshots: > > Datastax OpsCenter : > http://img4.imageshack.us/img4/2528/datastaxopscenterheighr.png > or > AWS console : > http://img59.imageshack.us/img59/5223/ec2managementconsole.png > > I have tried to see what is read from any nodes with "inotifywatch -r > -t300 /raid0 > inotifywatch5min" and get the following result: > > root@ip-10-64-177-38:~# cat inotifywatch5min > total access close_nowrite open filename > 234580 113280 60691 60609 > /raid0/cassandra/data/cassa_teads/data_viewer/ > 56013 27108 14454 14451 > /raid0/cassandra/data/cassa_teads/data_ip_viewer/ > 30748 14998 7884 7866 > /raid0/cassandra/data/cassa_teads/algo_ad_newcapping/ > 301 147 76 78 > /raid0/cassandra/data/cassa_teads/data_transac/ > 191 95 48 48 > /raid0/cassandra/data/cassa_teads/data_cust_website_viewer/ > 6 0 3 3 /raid0/cassandra/ > 2 0 1 1 > /raid0/cassandra/data/ > 2 0 1 1 > /raid0/cassandra/commitlog/ > 2 0 1 1 > /raid0/cassandra/saved_caches/ > > > root@ip-10-250-202-154:~# cat inotifywatch5min > total access modify close_write close_nowrite open moved_from > moved_to create delete filename > 307378 115456 77706 12 57119 57035 > /raid0/cassandra/data/cassa_teads/data_viewer/ > 55395 26878 0 0 14259 14258 > /raid0/cassandra/data/cassa_teads/data_ip_viewer/ > 36155 17653 0 0 9256 9246 > /raid0/cassandra/data/cassa_teads/algo_ad_newcapping/ > 7377 188 7153 6 4 11 > /raid0/cassandra/data/cassa_teads/data_action/ > 401 0 364 6 4 12 > /raid0/cassandra/data/cassa_teads/stats_ad_uv/ > 244 120 0 0 62 62 > /raid0/cassandra/data/cassa_teads/data_transac/ > 160 76 0 0 42 42 > /raid0/cassandra/data/cassa_teads/data_cust_website_viewer/ > 26 0 0 0 13 > 13 /raid0/cassandra/data/cassa_teads/ > 12 0 2 2 1 > 3 /raid0/cassandra/commitlog/ > 6 0 0 0 3 > 3 /raid0/cassandra/ > 2 0 0 0 1 > 1 /raid0/cassandra/data/ > 2 0 0 0 1 > 1 /raid0/cassandra/saved_caches/ > > > root@ip-10-64-167-32:~# cat inotifywatch5min > total access modify close_write close_nowrite open filename > 218489 105379 0 0 56615 56495 > /raid0/cassandra/data/cassa_teads/data_viewer/ > 61553 29733 0 0 15911 15909 > /raid0/cassandra/data/cassa_teads/data_ip_viewer/ > 33262 16214 0 0 8528 8520 > /raid0/cassandra/data/cassa_teads/algo_ad_newcapping/ > 407 0 370 6 4 12 > /raid0/cassandra/data/cassa_teads/stats_ad_uv/ > 280 134 0 0 73 73 > /raid0/cassandra/data/cassa_teads/data_transac/ > 163 79 0 0 42 42 > /raid0/cassandra/data/cassa_teads/data_cust_website_viewer/ > 17 0 3 3 1 > 4 /raid0/cassandra/commitlog/ > 8 0 0 0 4 > 4 /raid0/cassandra/data/cassa_teads/ > 6 0 0 0 3 > 3 /raid0/cassandra/ > 2 0 0 0 1 > 1 /raid0/cassandra/data/ > 2 0 0 0 1 > 1 /raid0/cassandra/saved_caches/ > > I see no reason to have a md0 disk read throughput up to 8 time bigger on > the .38 node... > > root@ip-10-64-167-32:~# iostat -mx 5 100 > > Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz > avgqu-sz await svctm %util > xvdap1 0.00 0.40 0.20 0.40 0.00 0.00 18.67 > 0.00 6.67 6.67 0.40 > xvdb 3.60 0.00 471.60 0.00 13.48 0.00 58.53 > 33.31 69.58 1.79 84.20 > xvdc 3.40 0.00 474.40 0.00 13.76 0.00 59.42 > 30.06 62.63 1.72 81.60 > xvdd 2.60 0.00 478.20 0.00 13.69 0.00 58.61 > 28.74 61.74 1.76 84.40 > xvde 3.40 0.00 472.40 0.00 13.34 0.00 57.82 > 23.08 47.96 1.74 82.40 > md0 0.00 0.00 1954.20 0.00 55.57 0.00 58.24 > 0.00 0.00 0.00 0.00 > > avg-cpu: %user %nice %system %iowait %steal %idle > 11.95 11.88 11.54 48.33 0.20 16.10 > > Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz > avgqu-sz await svctm %util > xvdap1 0.00 2.40 0.40 1.00 0.00 0.01 25.14 > 0.15 110.00 55.71 7.80 > xvdb 3.40 0.00 481.60 63.20 13.94 2.59 62.13 > 33.79 62.86 1.56 84.80 > xvdc 3.60 0.00 469.20 64.40 13.43 2.68 61.81 > 40.35 76.23 1.54 82.40 > xvdd 6.60 0.20 480.80 64.40 13.93 2.65 62.28 > 45.99 84.72 1.63 88.60 > xvde 6.60 0.00 482.00 65.60 14.20 2.68 63.14 > 48.76 89.77 1.61 88.00 > md0 0.00 0.00 1910.80 257.80 54.92 10.60 61.88 > 0.00 0.00 0.00 0.00 > > avg-cpu: %user %nice %system %iowait %steal %idle > 12.41 12.82 10.93 36.15 0.21 27.48 > > Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz > avgqu-sz await svctm %util > xvdap1 0.00 0.60 2.40 0.60 0.03 0.00 23.47 > 0.18 58.67 24.67 7.40 > xvdb 3.80 0.00 429.20 4.80 12.41 0.20 59.48 > 16.44 37.94 1.70 73.80 > xvdc 3.00 0.00 432.60 4.80 12.47 0.20 59.33 > 20.74 47.44 1.71 75.00 > xvdd 2.20 0.00 439.60 4.80 12.56 0.20 58.80 > 17.57 39.44 1.78 79.20 > xvde 2.00 0.00 449.20 3.60 12.84 0.15 58.73 > 15.96 35.29 1.68 76.00 > md0 0.00 0.00 1744.40 18.00 49.63 0.75 58.55 > 0.00 0.00 0.00 0.00 > > Did anyone experiments something similar ? > > How can I dig further to see what is wrong ? > > Any idea on what on C* can be responsible of this king of targeted reads ? > > Alain > > >
