Swap and Performance Time Windows
Symmetrix Optimizer utilizes time windows to schedule swaps and to indicate what time samples are to be used for the analysis process. By default, Optimizer will include all samples in its analysis. Note that the default swap time window is set to exclude; no swaps will be performed until the swap time window is changed.
Use the performance time windows to identify your business cycle and to specify date and time ranges (past or future) when samples will be included in or excluded from the Symmetrix Optimizer analysis. By default, all performance information is used, due to a default time window.
Use the swap time windows to specify date and time ranges when swaps are allowed or not allowed to start. The Symmetrix Optimizer will never start a swap session less than 30 minutes before the end of an inclusion swap time window; however, a swap that has started may continue beyond the specified time window.
Use the swap time windows to carefully plan swap sessions and to minimize impact on performance of critical workloads. Although the swap process runs in low priority, it might introduce some overhead on the Symmetrix back end. Reducing the maximum number of simultaneous swaps and using the quality of service (QoS) copy-pacing feature are other ways to minimize the overhead of Optimizer swaps.
Time windows are hierarchical in nature and can be either periodic or non-periodic. If multiple time windows have time ranges that overlap one another, the higher-listed time window will override the others. Therefore, the order of time windows in the list resolves conflicts between overlapping time windows; conflict resolution only applies to time windows of the same type.
Swap and performance time windows both have one default time window. The default time window can be set to either inclusion or exclusion. Use this feature to simplify the time window definitions.
When in SMC, use the client local time to set time windows. Conversion of time zone is done automatically by the Optimizer server.
The Symmetrix Optimizer collects and saves performance data regardless of the performance time window definitions; these definitions are only relevant for the analysis process. As a result, analysis data is always available, and there is no need to collect new statistics when a new time window is defined.
Time windows that span over the day in which daylight savings time is defined may be off by one hour. The best practice is to define two separate time windows—one for winter and one for summer.
Setting Swap and Performance Time Windows from SMC The lower table in Figure 12 is an editable summary of either the Performance or Swap Time Windows.
EMC Symmetrix Optimizer A Detailed Review