Monitoring performance when capacity saving is in use

When your site implements capacity saving with deduplication and compression, you'll need to monitor peformance. If there are performance issues, there are steps you can take to resolve them.

The following table outlines the best practices for items that can be monitored when deduplication and compression is used.

Monitored item	Description
Performance	Verify the throughput for DRD-VOLs: Throughput for each DRD-VOL Total throughput for DRD-VOLs belonging to the same MP Unit. Total throughput for DRD-VOLs in a storage system. When the performance requirements are not met, you can change the capacity saving setting or expand the pool capacity.
Pool capacity monitoring	Check whether the used pool capacity exceeds the threshold. When the capacity exceeds the threshold, check the amount of system data (amount of garbage data). If the amount of garbage data is small, you should expand the pool capacity.

Use the following workflow to detect and troubleshoot performance issues associated with the capacity saving function.

Additional details for steps 1-5 of the performance assessment workflow.

1. Identify the pools or the volumes for which performance is insufficient. Any of the following conditions can indicate that there is a performance issue:
   • The current throughput is lower than the required throughput.
   • The average write throughput of DRD-VOL in the operation cycle is greater than the garbage collection performance of each DRD-VOL
   • The average write throughput of each MP unit in the operation cycle is greater than the garbage collection performance of each MP unit
   • The average write throughput of each system in the operation cycle is greater than the garbage collection performance of each system
2. Check the settings for the capacity saving function. When insufficient performance has been detected, check the following capacity saving settings: If they are correct, go to step 3.
   • If the capacity saving setting is set to Compression or Deduplication or Compression by mistake, disable the capacity saving setting.
   • If the capacity saving mode is set to Inline by mistake, change it to Post process. For details how to change the capacity saving mode, see Command Control Interface Command Reference.
3. Check if the used pool capacity exceeds the threshold. Check if the Pool Usage exceeds the warning threshold of the pool. If the pool usage exceeds the threshold, a SIM is issued. When performance is insufficient--even if the settings are as designed--it is likely that the pool capacity will soon be full, and garbage collection is prioritized over I/O.
   • If the threshold is exceeded, go to step 4.
   • If the threshold is not exceeded, go to step 5.
4. Check the percentage of the amount of system data. Check [the amount of system data](divided by the amount of garbage data)].
   • When the percentage of system data in the used pool capacity is higher than 10%:

     If you know that garbage data is increased only temporarily, and time required for recovering the performance is acceptable, wait until the performance is recovered. If it is not acceptable, expand the pool capacity.

     When the percentage of system data in the used pool capacity is higher than 10%, if garbage data is collected by garbage collection, the pool usage is lower than the threshold. When it is lower than the threshold, the priority of garbage collection is lowered, and I/O performance is recovered.

   • When the percentage of system data in the used pool capacity is lower than 10%:

     To prioritize I/O processing, expand the pool capacity. Although the garbage data that should be collected is small, the priority of garbage collection is high.

5. Decide whether the capacity saving function should be used:
   • When garbage collection is not effective, and performance is not sufficient, dedupe and compression cannot be applied to the volume. If there is any volume for which the capacity saving setting can be disabled, disable it.
   • The used capacity of the pool increases when the capacity saving setting is disabled. Confirm in advance that the pool has enough free capacity.