After sending this message I issued the iostat -dxm 5 command on the DNs.... the %util column shows 70-80 average value sometimes going up to 90-100 for few seconds
Does this mean the disk is becoming the bottleneck ? or is this normal ? On Thu, Aug 23, 2012 at 3:14 PM, Himanish Kushary <himan...@gmail.com>wrote: > Hi, > > I am curious about interpretation of the output from iostat on a datanode > during a M/R run.I want to understand how to diagnosis a disk i/o issue in > a hadoop cluster. > > Is there any good documentation to help me understand the results from > iostats in Hadoop context ? > > Here are the iostat output from a DN while two intensive M/R jobs were > executing.Does this result indicate any performance issue related to the > disks ? > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 1.80 0.00 59.20 0 296 > sdb 1436.20 96376.00 211424.00 481880 1057120 > > avg-cpu: %user %nice %system %iowait %steal %idle > 22.81 0.00 45.28 3.59 0.00 28.32 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 2.80 25.60 80.00 128 400 > sdb 1073.60 45891.20 203473.60 229456 1017368 > > avg-cpu: %user %nice %system %iowait %steal %idle > 17.28 0.00 74.49 0.32 0.00 7.92 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 3.44 0.00 83.97 0 440 > sdb 1174.62 52370.99 209789.31 274424 1099296 > > avg-cpu: %user %nice %system %iowait %steal %idle > 51.72 0.00 47.60 0.31 0.00 0.38 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 1.20 0.00 22.40 0 112 > sdb 1094.20 67492.80 177187.20 337464 885936 > > avg-cpu: %user %nice %system %iowait %steal %idle > 43.73 0.00 36.19 3.03 0.00 17.05 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 1.80 0.00 46.40 0 232 > sdb 1241.20 100969.60 162806.40 504848 814032 > > avg-cpu: %user %nice %system %iowait %steal %idle > 37.09 0.00 58.61 0.77 0.00 3.54 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 4.60 182.40 19.20 912 96 > sdb 1235.20 47780.80 235912.00 238904 1179560 > > avg-cpu: %user %nice %system %iowait %steal %idle > 47.23 0.00 42.49 3.09 0.00 7.19 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 1.60 0.00 46.40 0 232 > sdb 1005.20 86502.40 135886.40 432512 679432 > > > > --------------------------- > Thanks & Regards > Himanish > -- Thanks & Regards Himanish
