It can be useful to compare the performance of similar activities if, for example, you suspect that a job is performing differently than other similar jobs that have run in the past.

The Compare tab shows you the performance of the selected job compared with the performance of other similar jobs. Cloudera Manager identifies jobs that are similar to each other (jobs that are basically running the same code – the same Map and Reduce classes, for example).

To compare an activity to other similar activities:

1. Select the job or activity from the Activities list.
2. Click the Compare tab.

The activity comparison feature compares performance and resource statistics of the selected job to the mean value of those statistics across a set of the most recent similar jobs. The table provides visual indicators of how the selected job deviates from the mean calculated for the sample set of jobs, as well as providing the actual statistics for the selected job and the set of the similar jobs used to calculate the mean.

• The first row in the comparison table displays a set of visual indicators of how the selected job deviates from the mean of all the similar jobs (the combined Average values). This is displayed for each statistic for which a comparison makes sense. The diagram in the ID column shows the elements of the indicator, as follows:
  • The line at the midpoint of the bar represents the mean value of all similar jobs. The colored portion of the bar indicates the degree of deviation of your selected job from the mean. The top and bottom of the bar represent two standard deviations (plus or minus) from the mean.
  • For a given metric, if the value for your selected job is within two standard deviations of the mean, the colored portion of the bar is blue.
  • If a metric for your selected job is more than two standard deviations from the mean, the colored portion of the bar is red.
• The following rows show the actual values for other similar jobs. These are the sets of values that were used to calculate the mean values shown in the Combined Averages row. The most recent ten similar jobs are used to calculate the average job statistics, and these are the jobs that are shown in the table.