When you create or edit a pool, you set the Dynamic Tiering monitoring mode: period mode, or continuous mode. When you change the monitoring mode, the new monitoring setting becomes effective when the next monitoring period starts.

Period mode (default)

When Period mode is enabled, tier range values and page relocations are determined based solely on the monitoring data from the last complete cycle. Relocation is performed according to any changes in I/O loads. However, if the I/O loads vary greatly, relocation might not finish in one cycle.

Continuous mode

When Continuous mode is enabled, the weighted average efficiency is calculated by weighting the latest monitoring information and the collected monitoring information in the past cycles. By performing the tier relocation based on the weighted average efficiency, even if a temporary decrease or an increase of the I/O load occurs, unnecessary relocation can be avoided.

Cautions when using monitoring modes

• When Continuous monitoring mode is used, best practice is to collect monitoring information using the following execution modes:
  • Auto execution mode
  • Manual execution mode with collecting the periodic monitoring information by defining a script using RAID Manager

  If Manual execution mode is used without scripts, Continuous monitoring mode can be set. However, in this case, unexpected results might be calculated because the weighted average efficiency is calculated based on very different duration (short and long) periods information obtained in the past cycles.

• When Continuous monitoring mode is used, the frequency distributions are displayed for each pool and V-VOL calculated by using the monitor value on which the weighted calculation is done.

  These calculated values are the predictive values for the next cycle after successfully relocating all pages. Therefore, these values might differ from an actual monitoring result when they appear.

  In Performance Utilization of each tier, regardless of the type of the monitoring mode setting, the monitor values that were already collected in the current cycle are displayed.

  If you switch the monitoring mode from Period to Continuous or from Continuous to Period, the current cycle's monitoring data that is being collected is not discarded. However, the data calculated by using past monitor cycle information on which the weighted calculation is done will be reset.