Cache policies and configurations are involved in storage-layer performance optimization of Huawei flash storage.

Cache watermarks in Huawei flash storage systems manage dirty data flushing. The *HCIP-Storage V5.5 Training Material (Module 5: Storage System Maintenance and Troubleshooting)* explains:

- Option A: True. “The low watermark for dirty data should be around 20% to ensure sufficient buffer space.”

- Option B: True. “The high watermark should not be too high, and the gap between high and low watermarks should be sufficient to avoid frequent flushing.”

- Option C: True. “A high watermark that is too high causes I/O fluctuations and increased latency during traffic bursts.”

- Option D: False. “High watermarks affect write performance by delaying flushes, but low watermarks do not directly impact read performance, which depends on prefetch and cache hit ratios.”

Thus, option D is false.