I don't think it necessarily means that the job is a bad candidate for MR. It's a different type of a workload. Hortonworks has a great article on the different types of workloads you might see and how that affects your provisioning choices at http://docs.hortonworks.com/HDPDocuments/HDP1/HDP-1.3.2/bk_cluster-planning-guide/content/ch_hardware-recommendations.html
I have not looked at the Grep code so I'm not sure why it's behaving the way it is. Still curious that streaming has a higher IO throughput and lower CPU usage. It may have to do with the fact that /bin/grep is a native implementation and Grep (Hadoop) is probably using Java Pattern/Matcher api. On Thu, Oct 10, 2013 at 12:29 PM, Xuri Nagarin <secs...@gmail.com> wrote: > Thanks Pradeep. Does it mean this job is a bad candidate for MR? > > Interestingly, running the cmdline '/bin/grep' under a streaming job > provides (1) Much better disk throughput and, (2) CPU load is almost evenly > spread across all cores/threads (no CPU gets pegged to 100%). > > > > > On Thu, Oct 10, 2013 at 11:15 AM, Pradeep Gollakota > <pradeep...@gmail.com>wrote: > >> Actually... I believe that is expected behavior. Since your CPU is pegged >> at 100% you're not going to be IO bound. Typically jobs tend to be CPU >> bound or IO bound. If you're CPU bound you expect to see low IO throughput. >> If you're IO bound, you expect to see low CPU usage. >> >> >> On Thu, Oct 10, 2013 at 11:05 AM, Xuri Nagarin <secs...@gmail.com> wrote: >> >>> Hi, >>> >>> I have a simple Grep job (from bundled examples) that I am running on a >>> 11-node cluster. Each node is 2x8-core Intel Xeons (shows 32 CPUs with HT >>> on), 64GB RAM and 8 x 1TB disks. I have mappers set to 20 per node. >>> >>> When I run the Grep job, I notice that CPU gets pegged to 100% on >>> multiple cores but disk throughput remains a dismal 1-2 Mbytes/sec on a >>> single disk on each node. So I guess, the cluster is poorly performing in >>> terms of disk IO. Running Terasort, I see each disk puts out 25-35 >>> Mbytes/sec with a total cluster throughput of above 1.5 Gbytes/sec. >>> >>> How do I go about re-configuring or re-writing the job to utilize >>> maximum disk IO? >>> >>> TIA, >>> >>> Xuri >>> >>> >>> >> >
