Following ingest, if an ILM rule includes instructions to make erasure coded copies of object data, the applicable erasure coding scheme breaks object data into data and parity fragments and distributes these fragments across the configured storage pool's Storage Nodes.
Data flow
The ILM engine, which is a component of the LDR, controls erasure coding and ensures that the Erasure Coding profile is applied to object data.
- The ILM engine queries the ADC service to determine which DDS service can best perform the erasure coding operation. Once determined, the ILM engine sends an "initiate" request to that service.
- The DDS service instructs an LDR to erasure code the object data.
- The source LDR service sends a copy to the LDR service selected for erasure coding.
- Once broken into the appropriate number of parity and data fragments, the LDR service distributes these fragments across the Storage Nodes (LDR services) that make up the Erasure Coding profile’s storage pool.
- The LDR service notifies the ILM engine, confirming that object data is successfully distributed.
- The ILM engine updates the DDS service with object location metadata.
Erasure coding related attributes
The table shows the primary attributes used to track an erasure coded object:
| Component | Attribute changes |
|---|---|
| Evaluations: The total number of ILM evaluations that have been performed to date increases by one. | |
Object Data: The size of erasure coded fragments stored on the object store increases by an amount roughly equivalent to the object's size plus the erasure coding overhead. |