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docs: remove stale delta NCCL recommendation #2312

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zhuzilin merged 1 commit into from
Aug 24, 2026
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docs: remove stale delta NCCL recommendation #2312

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3 changes: 2 additions & 1 deletion docs/en/advanced/external-rollout-engines.md
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Expand Up @@ -14,9 +14,10 @@ This page is a roadmap. Use it to decide when to use `--rollout-external-engine-
| Trainer and external engines cannot form an NCCL group, but can see the same filesystem path | `--update-weight-mode full --update-weight-transport disk` |
| Full checkpoints are too heavy for large-model cross-cluster or cross-DC sync | `--update-weight-mode delta --update-weight-transport disk` |
| Rollout serving can use an independent SGLang environment, or even different GPU models/vendors | external engines + disk transport |
| You want to validate delta wire/apply logic inside one datacenter | `--update-weight-mode delta --update-weight-transport nccl` |
| You need frozen reference, reward, or tool-side models | Prefer `update_weights: false` in [SGLang Config](sglang-config.md#3-multi-model-serving) |

Delta mode supports disk transport only. Use full mode when syncing weights over NCCL.

## What External Engine Does

First launch SGLang servers independently:
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3 changes: 2 additions & 1 deletion docs/zh/advanced/external-rollout-engines.md
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Expand Up @@ -14,9 +14,10 @@ External rollout engine 指的是：SGLang engine 不由 slime 训练任务启
| 训练器和 external engine 不能建立 NCCL group，但能共享同一路径的文件系统 | `--update-weight-mode full --update-weight-transport disk` |
| 大模型跨集群或跨数据中心同步，full checkpoint 太重 | `--update-weight-mode delta --update-weight-transport disk` |
| rollout serving 想使用独立 SGLang 环境，甚至不同型号或不同厂家的 GPU | external engine + disk transport |
| 想验证 delta wire/apply 逻辑，但仍在同一数据中心内 | `--update-weight-mode delta --update-weight-transport nccl` |
| 需要 reference、reward、tool-side model 等冻结模型 | 优先用 [SGLang Config](sglang-config.md#3-多模型服务) 的 `update_weights: false` |

delta mode 仅支持 disk transport。通过 NCCL 同步权重时请使用 full mode。

## External Engine 做了什么

使用 external engine 时，先独立启动 SGLang server：
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