You can choose one of these load balance policies to optimize I/O performance:• Round-robin with subset — The round-robin with subset I/O load balance policy routes I/O requests, in rotation,to each available data path to the RAID controller module that owns the virtual disks. This policy treats all pathsto the RAID controller module that owns the virtual disk equally for I/O activity. Paths to the secondary RAIDcontroller module are ignored until ownership changes. The basic assumption for the round-robin policy is thatthe data paths are equal. With mixed host support, the data paths may have different bandwidths or differentdata transfer speeds.• Least queue depth with subset — The least queue depth with subset policy is also known as the least I/Os orleast requests policy. This policy routes the next I/O request to a data path that has the least outstanding I/Orequests queued. For this policy, an I/O request is simply a command in the queue. The type of command or thenumber of blocks that are associated with the command are not considered. The least queue depth with subsetpolicy treats large block requests and small block requests equally. The data path selected is one of the paths inthe path group of the RAID controller module that owns the virtual disk.• Least path weight with subset (Windows operating systems only) — The least queue depth with subset policy isalso known as the least I/Os or least requests policy. This policy routes the next I/O request to a data path thathas the least outstanding I/O requests queued. For this policy, an I/O request is simply a command in the queue.The type of command or the number of blocks that are associated with the command are not considered. Theleast queue depth with subset policy treats large block requests and small block requests equally. The data pathselected is one of the paths in the path group of the RAID controller module that owns the virtual disk.Monitoring System PerformanceYou can use the Performance Monitor to select virtual disks and RAID controller modules to monitor or to change thepolling interval.Keep these guidelines in mind when using the Performance Monitor:• The Performance Monitor does not dynamically update its display if any configuration changes occur while thewindow is open. You must close the Performance Monitor window and reopen it for the changes to bedisplayed.• Using the Performance Monitor to retrieve performance data can affect the normal storage array performancedepending on the polling interval that you set.• If the storage array you are monitoring begins in or transitions to an unresponsive state, an informational dialogis displayed. The dialog informs you that the Performance Monitor cannot poll the storage array for performancedata.You can view data for select virtual disks and RAID controller modules in tabular format or in graphical format.• Table view — The data is presented in a tabular format. For more information on the data presented in the table,see the online help.• Graphical View — The data is presented with a single x-axis and a single y-axis. The x-axis represents the timefor which you selected to view performance data. The y-axis represents the metric you selected on the DefineGraph window. A curve on the graph represents the value of the metric over time for a particular device. Ahistorical graph can contain up to four curves. A real-time graph is limited to a single curve. For the real-timedata graph, the data points refresh every 5 seconds. The system drops the oldest data point from the graph andadds the newest data point to the graph. For historical data graphs, the data points are static.Monitoring Performance Using The Tabular ViewTo monitor the performance of the arrays using the tabular view:1. In the AMW, select Monitor → Health → Monitor Performance → Table View.The Performance Monitor window is displayed.2. Click Settings.3. Select the items that you want to monitor.29
