It does not appear to affect the response time, certainly not in a positive way.
2012/1/5 Philippe <[email protected]> > What if you shutdown the cassandra service on the slow node, does that > improve your read performance ? > If it does then that sole node is responsible for the slow down because it > can't act as a coordinator fast enough. > > 2012/1/5 R. Verlangen <[email protected]> > > I'm also reading with CL = ONE >> >> >> 2012/1/5 Philippe <[email protected]> >> >>> Depending on the CL you're reading at it will yes : if the CL requires >>> that the "slow" node create a digest of the data and send it to the >>> coordinator then it might explain the poor performance on reads. What is >>> your read CL ? >>> >>> 2012/1/5 R. Verlangen <[email protected]> >>> >>> As I posted this I noticed that the other node's CPU is running high on >>>> some other cronjobs (every couple of minutes to 60% usage). Is the lack of >>>> more CPU cycles a problem in this case? >>>> >>>> Robin >>>> >>>> 2012/1/5 R. Verlangen <[email protected]> >>>> >>>> CPU is idle (< 10% usage). Disk reads occasionally blocks over 32/64K. >>>>> Writes around 0-5MB per second. Network traffic 0.1 / 0.1 MB/s (in / out). >>>>> Paging 0. System int ~ 1300, csw ~ 2500. >>>>> >>>>> >>>>> 2012/1/5 Philippe <[email protected]> >>>>> >>>>>> What can you see in vmstat/dstat ? >>>>>> Le 5 janv. 2012 11:58, "R. Verlangen" <[email protected]> a écrit : >>>>>> >>>>>> Hi there, >>>>>>> >>>>>>> I'm running a cassandra 0.8.6 cluster with 2 nodes (in 2 DC's), RF = >>>>>>> 2. Actual data on the nodes is only 1GB. Disk latency < 1ms. Disk >>>>>>> throughput ~ 0.4MB/s. OS load always below 1 (on a 8 core machine with >>>>>>> 16GB >>>>>>> ram). >>>>>>> >>>>>>> When I'm running my writes against the cluster with cl = ONE all >>>>>>> reads appear to be faster then the writes. >>>>>>> >>>>>>> Average write speed = 1600us/operation >>>>>>> Average read speed = 200us/operation >>>>>>> >>>>>>> I'm really wondering why this is the case. Anyone got a clue? >>>>>>> >>>>>>> With kind regards, >>>>>>> Robin >>>>>>> >>>>>> >>>>> >>>> >>> >> >
