Capacity reporting changes for devices that use hardware compression

For storage systems that use hardware compression, as of Q4 2020 capacity usage is now reported based on the physical capacity rather than the effective capacity of the storage system.

The devices affected by this update are:
  • Storage systems such as FlashSystem 9100, FlashSystem 900, and Storwize® V7000 Gen3, which contain IBM FlashCore® Modules with hardware compression
  • SAN Volume Controller and Storwize storage systems that are configured as storage virtualizers, and which use back-end storage systems with hardware compression

Two sets of capacity values are now shown for storage systems and pools. To help you see whether you are running out of space, the existing capacity columns, such as Pool Capacity (GiB), and Physical Allocation (%), now show physical capacity values. New columns were added to show the effective capacity based on the data reduction savings that are achieved with hardware compression.

The following features and values are affected:
  • In capacity views, reports, and charts, you'll see a sharp drop in the values for capacity because capacity is now reported based on physical capacity.
  • Alert thresholds might need to be adjusted for storage systems and pools.
  • Capacity values such as shortfall percentage and zero capacity now use physical capacity rather than effective capacity.
    Zero Capacity: Because the reporting of physical capacity values has changed, wait about seven days before you check the projected values for zero capacity. The estimation of zero capacity is based on historical usage trends.

Alert updates

This update affects capacity alerts for storage systems and pools in IBM® Storage Insights Pro. After the update completes, you'll see a sharp drop in the reported capacity values and that might cause the following alerts to trigger:
  • Pool Capacity
  • Physical Allocation
  • Available Pool Space
  • Allocated Space
Review the alert threshold values for block storage systems and pools. Since the capacity values are now based on physical capacity, you might want to reduce the threshold value at which the alerts fire for your affected devices.

New alerts are available to monitor the effective capacity values. Check for alerts that begin with Effective.

Pro tip: For devices that use hardware compression, you can now define alerts to monitor physical capacity at the pool level. Previously, it was only possible to monitor physical capacity at the RAID array level.

Changes to capacity columns for block storage systems and pools

Block Storage Systems page
The following screen capture shows the capacity columns that were updated to show the physical capacity of the device, rather than the effective capacity.
Block Storage Systems page showing the physical capacity values. Previously, these columns showed effective capacity values.
The effective capacity information is still available. New columns were added to the Block Storage Systems page to show the effective capacity based on the data reduction savings that are achieved with hardware compression. The following table shows the original capacity columns and the corresponding columns that were added to show the original effective values:
Original columns show physical capacity New columns show effective capacity
Pool Capacity (GiB) Effective Capacity (GiB)
Physical Allocation (%) Effective Used Capacity (%)
Available Pool Space (GiB) Effective Available Capacity (GiB)
Allocated Space (GiB)  
Used Pool Space (GiB) Effective Used Capacity (GiB)
Tip: There is no corresponding Effective column for Allocated Space (GiB). The value is similar to Effective Used Capacity (GiB) which also includes the pool overhead space.
Pools page
The following screen capture shows the capacity columns that were updated to show the physical capacity, rather than the effective capacity.
Pools page showing the physical capacity values. Previously, these columns showed effective capacity values.
The effective capacity information is still available. New columns were added to the Pools page to show the effective capacity based on the data reduction savings that are achieved with hardware compression. The following table shows the original capacity columns and the corresponding columns that were added to show the original effective values:
Original columns show physical capacity New columns show effective capacity
Capacity (GiB) Effective Capacity (GiB)
Physical Allocation (%) Effective Used Capacity (%)
Available Pool Space (GiB) Effective Available Capacity (GiB)
Allocated Space (GiB)  
Used Space (GiB) Effective Used Capacity (GiB)
Tips:
  • There is no corresponding Effective column for Allocated Space (GiB). The value is similar to Effective Used Capacity (GiB) which also includes the pool overhead space.
  • The Unallocated Volume Space (GiB) column was renamed to Effective Unallocated Volume Space (GiB). The value that is shown in the GUI is not changed.

Changes to historical charting

In historical capacity charts for storage systems and pools, you'll see a sharp drop in the values for capacity, allocated space, and available pool space. That's because capacity values are now measured based on the physical capacity rather than the effective capacity. Before, for example, the capacity value measured for your device was 250 TiB. Now it's 100 TiB. That's because the capacity savings achieved by hardware compression are no longer included when capacity is measured.

In the following chart, the blue vertical line represents the point at which IBM Storage Insights is updated.

The chart values before the update represent the effective capacity, which includes data reduction savings; the values after the update represent the physical capacity, which is lower.

Chart showing storage system capacity values before and after the IBM Storage Insights update. A blue vertical line on the chart marks the point of the upgrade.

The effective capacity metrics are still available. To add the metrics to the chart, click Select Chart Metrics Select chart metrics and add the metrics that begin with Effective.

Changes to capacity overview chart

The Physical Capacity chart for storage systems now shows physical capacity values rather than effective capacity. After the update, you'll see a sharp drop in the allocated, unallocated, and total space values that are shown on the chart.

Physical Capacity chart on the Overview page for a storage system