Re-image a storage processor (SP) to safely fix problems with the system software that could not be resolved by rebooting the SP. Re-imaging analyzes the system software for errors and attempts to correct them instantly. Re-image an SP from the Service System page.
Your configuration settings and stored files will not be changed.
References:
https://community.emc.com/docs/DOC-40315

Explanation/Reference:
The technology used for snapshots of both block and file resources in Unity is called redirect on write.

Explanation:
The Battery Backup Unit (BBU) provides power to the Storage Processor in the event that cabinet power is lost. The BBU is designed to power the SP long enough for the system to store SP cache content to the M.2 SSD device before powering down. The BBU includes sensors which communicate its charge and health status to the SP. In the event the BBU is discharged the SP will disable cache until the BBU has recharged. In the event the BBU has faulted or cannot sustain enough charge, an alert will be generated.
References:
https://www.emc.com/collateral/white-papers/h15084-dell-emc-unity-introduction-to-the-platform.pdf

https://www.dellemc.com/resources/en-us/asset/white-papers/products/storage/h17122- dell_emc_unity-dr_access_and_testing.pdf