Expert Oracle Exadata - Parent Directory

CHAPTER 12 MONITORING EXADATA PERFORMANCEFigure 12-11. Selecting a “highest-average” chart for monitoring cells with highest read I/O requestsTo see the cell metrics available, you’ll have to select Oracle Exadata Storage Server as the chart type andpick one of the metrics to show. You probably want to use the Group Statistics for monitoring the wholecell group as a starting point, instead of monitoring all 14 storage cells (in a full rack) separately. Thegroup statistics allow you to sum together stats from all the cells in the group (when monitoring totaldisk I/O throughput, for example) or show minimum, maximum, averages and standard deviationacross all cells (when monitoring average disk I/O response times, for example). Pay attention to whatthe metric means and which aggregation operations make sense for a given metric. For example, itdoesn’t make much sense to display the sum of all average disk I/O response times in a chart. Themetrics starting with Avg show average values over multiple objects monitored. For example, the AvgCelldisk Reads (MB) monitors average megabytes read per celldisk. On the other hand, the Total CelldiskReads (MB) metric sums together the MB read by all cell disks in a cell. And now if you use the GroupStatistics option to monitor multiple cells, you should use Sum to see the total MB read from cell disksacross all cells and Average or Min/Max to see the average per cell or a cell with the smallest or biggestMB read cell disk throughput.If you do want to monitor individual cells— for example, the two storage cells with the worst offloadefficiency—then you can either define a separate offloading efficiency chart for each cell (and end upwith 14 charts in a full rack configuration) or you can select Targets With Lowest Average as the charttype, as shown in Figure 12-12.398