Walk me through how you would checkpoint a 70B model tr...

Checkpointing a 70B model requires a robust strategy: utilize ZeRO-3 sharding to distribute the load, and employ async host-RAM staging to move data to NVMe in the background to minimize blocking. It is critical to save the data loader cursor and RNG state alongside model weights to ensure reproducibility. Finally, implement per-rank checksum validation to ensure data integrity and maintain a three-generation rolling retention policy to protect against corruption.