question MapReduce Job stuck in Reduce Phase in Support Questions

question MapReduce Job stuck in Reduce Phase in Support Questions https://community.cloudera.com/t5/Support-Questions/MapReduce-Job-stuck-in-Reduce-Phase/m-p/25645#M34980 Hello all, I've installed a new cluster using managed installation of cdh 5 with 7 dedicated and hardware specific machines. The installation was succesful and all health tests have been passed succesfully. Also I've tested that the network is fully operational, all ports can be accessed and the DNS is responding both direct and reverse. My problem raises when I try to run a Hadoop application from the command line, I know that this must be a configuration error as I have ran the same JAR in an Amazon EMR machine without problems many times. The problem is that hadoop get stuck when a certain step of the reduce phase is reached. No matter how many reduce tasks I configure for the job (from 1 to N), I can see in the application master that the running tasks are always in the same state: 28.13% RUNNING reduce > copy(27 of 32 at 1.30 MB/s) The systems seems not to have any traffic at all, but if let them run indefinitely the program finishes ans the results are ok, but in almost a 1000% of the usual required time. In addition, several errors are raised: shuffle error:exceeded max_failed_unique_matche : bailing out I've seen googling around that this seems to be a common problem in many hadoop installations, but I've checked everything in the configuration witout success. I would really appreciate it if anyone could point me in another direction. Please do not hesitate to request any additional information or logs. Cheers  Fri, 16 Sep 2022 09:24:30 GMT JacintoArias 2022-09-16T09:24:30Z