WAL积压严重

部署IOTDB 3C3D模式后，批量写入和单条写入wal积压严重，这个要怎么优化

Start by reproducing the reported IoTDB 3C3D deployment with both batch and single-row writes, then measure where the WAL backlog accumulates. Compare the write paths and collect the configuration and workload details needed to identify the bottleneck. Done means the cause is confirmed and a tested optimization or clear limitation is documented.

Written by the indexing model from the issue text.