Product : Dell EMC, PowerFlex [SDS]/3.5, Enterprise
Feature : Data Corruption Detection, Reads/Writes, Data Availability
Content Owner:  Herman Rutten
Disk scrubbing (software)
In-flight integrity checks
Persistent integrity checks
The Background Device Scanner constantly searches for, and fixes, device errors before they can affect the system, thus providing additional data reliability. The scanner runs in the background, not interrupting other Storage Pool activities (such as adding and removing volumes). When scanning is enabled for a Storage Pool, the scanner seeks out corrupted sectors in the devices in that pool. The scanner also provides SNMP reporting about errors found.

In-flight checksum protection is provided for data reads and writes. This feature addresses errors that change the payload during the transit through the PowerFlex system. PowerFlex protects data in-flight by calculating and validating the checksum value for the payload at both ends. The checksum protection mode can be applied per Storage Pool.

Persistent checksum protection is provided for all data that is stored in Fine Granularity (FG) storage pools by default. This cannot be changed. Fine Granularity (FG) layout saves checksum data before and after processing to guarantee data integrity (compressed or not). There are also system checksums for metadata.

PowerFlex 3.5 adds enhancements to:
- Fine Granularity (FG) data layout: metadata cache for higher FG performance,
- Medium Granularity (MG) data layout: checksum,
- Sub-device error handling for improved resiliency.