In Huawei flash storage, the integrated I/O stack of SAN and NAS can be divided...

The integrated I/O stack in Huawei flash storage systems, such as OceanStor Dorado, is divided into layers, with the space management layer handling metadata and resource allocation. The *HCIP-Storage V5.5 Training Material (Module 5: Storage System Maintenance and Troubleshooting)* states: “The space management layer is responsible for metadata operations and space allocation. Key performance concerns include the cache hit ratio of hot metadata, which affects access speed, and CPU usage for background metadata management tasks, which impacts system efficiency.” Let’s evaluate:

- Option A: Correct. The material confirms that the cache hit ratio for hot metadata is critical for reducing latency in the space management layer.

- Option B: Correct. High CPU usage in metadata management can bottleneck performance, as noted in the material.

- Option C: Incorrect. Failover for protocol receiving threads is a concern for the data service layer, not the space management layer.

- Option D: Incorrect. The prefetch algorithm’s hit ratio is relevant to the data service layer, not space management.

Thus, options A and B are the performance concerns.