PowerStore Capacity May Rapidly Decrease if Drive Count Falls Below or Equals RAID Width

Customers may observe a sudden drop in available capacity on their PowerStore system and free space may appear significantly reduced in certain conditions. For example, the total capacity dropped suddenly.

Scenario 1:
This occurs when the number of remaining drives in the system is less than the configured RAID width.
For example, in a system configured with 7 drives in a 4+2 RAID 6 setup, if two drives are removed or fail, only 5 drives remain. Since RAID 6 requires a minimum of 6 drives in this configuration, the system no longer meets the minimum drive requirement. In this case, all free capacity becomes unavailable by design.

Scenario 2:
This may also occur when the number of drives is equal to the RAID width and an NVRAM cache drive goes offline.
For instance, in a system with 19 drives configured as 16+2 RAID 6, if one drive and one NVRAM cache drive are offline, the system technically still meets the minimum drive requirement. However, due to the offline NVRAM cache drive, all free capacity becomes unavailable.
Note: This behavior has been addressed and resolved in PowerStore OS 4.0.

Ensure the system maintains a sufficient number of operational drives to meet or exceed the minimum drive requirements for the configured RAID level. If there are any hardware issues (e.g., failed drives or offline NVRAM cache drives), replace the affected components as soon as possible to prevent capacity loss.