HP StorageWorks MSA2012i HP StorageWorks 2000 Modular Smart Array Reference Gu - Page 110

Setting Snap Pool Policies and Thresholds Each snap pool has three policy levels that notify you when the snap pool is reaching decreasing capacity. Each policy level has an associated policy that specifies system behavior when an associated threshold value is reached. The following table summarizes the default thresholds and policies. You can set the Warning and Error thresholds and the Error and Critical policies. Policy Level Threshold Policy Warning 75% Notify Only. Error 90% Delete Oldest Snapshots. Critical 99% Delete Snapshots. Note - SMU notifies you of events based on your event notification settings. See "Configuring Event Notification" on page 53 for more information about how and under what conditions the system alerts you when specific events occur. Policy Trigger Behavior A policy might be triggered before it appears that a specified threshold has been reached. This is because a threshold percentage is based on the size of the snap pool, less a fixed amount of 750 Mbyte for internal use. This fixed amount guarantees that there is enough reserve space to store pending data for which the controller has space. The following example demonstrates policy trigger behavior: Snap pool size = 10,000 Mbyte (10 Gbyte) Snap pool reserve = 750 Mbyte Space available = 9,250 Mbyte Policy trigger set at default error level of 90% = 9,250 Mbyte x 0.9 = 8,325 Mbyte In the above example, the 90% trigger occurs at 8.325 Gbyte. If you did not take into account the amount of reserve space, you might expect the trigger to occur at 9 Gbyte (10 Gbyte x 0.9). For larger snap pools, the impact of this reserve space is less noticeable. 110 HP StorageWorks 2000 Family Modular Smart Array reference guide • August 2008