Multi-node serving on Dynamo
Qwen2.5-14B’s FP16 weights are about 29 GB, larger than one NVIDIA L4’s 23 GB, so
it serves across two nodes as a gang: a Leader and a Worker, one L4 each,
pipeline-parallel across the pair over an EFA fabric. On a
Dynamo cluster Grove
and the KAI Scheduler gang-schedule the two pods together, Modelplane composes them
as a Grove PodCliqueSet, and they load their weights peer-to-peer with NVIDIA
ModelExpress.
This is the getting started tour scaled to two
nodes: one larger model on a spec.stack: Dynamo cluster, with EFA and
ModelExpress for the gang.
Set up the platform first,
for the gateway and cloud credentials, then apply the manifests below.
Register a Dynamo cluster
The InferenceClass describes a single-L4 node, sized up from the getting started
tour’s for the larger model’s weights and with EFA for the fabric. The
InferenceCluster runs two of them, sets spec.stack: Dynamo so Modelplane
installs Grove and the KAI Scheduler, and sets fabric: EFA on the pool.
# EKS g6.8xlarge, one NVIDIA L4 per node, with EFA. A single L4 can't hold the
# 14B model, so the gang spans two nodes; EFA gives their cross-node traffic and
# ModelExpress's peer-to-peer weight transfer an RDMA fabric instead of plain
# TCP. Its 128 GiB of memory holds the weights as they load, and the 100 GB disk
# holds the vLLM image.
#
# Both the GPU and the EFA fabric are claim: DRA devices. A gang's nodeSelector
# requests both, so DRA binds one L4 and one EFA interface per pod. The EFA
# device is installed by the EFA DRA driver the Dynamo stack runs.
apiVersion: modelplane.ai/v1alpha1
kind: InferenceClass
metadata:
name: l4-1x-g6-efa
spec:
description: "EKS g6.8xlarge, 1x NVIDIA L4, EFA"
provisioning:
provider: EKS
eks:
instanceType: g6.8xlarge
diskSizeGb: 100
accelerator:
type: nvidia-l4
count: 1
devices:
- name: gpu
claim: DRA
driver: gpu.nvidia.com
deviceClassName: gpu.nvidia.com
count: 1
attributes:
architecture: { string: Ada Lovelace }
capacity:
memory: { value: "23034Mi" } # L4's real reported VRAM (not the nominal 24GB)
- name: efa
claim: DRA
driver: dra.net
deviceClassName: efa.networking.k8s.aws
count: 1
# An EKS cluster running the Dynamo serving stack, with a two-node L4 pool so a
# gang can span both nodes. spec.stack: Dynamo installs Grove and the KAI
# Scheduler, which gang-schedule the leader and worker together and compose them
# as a Grove PodCliqueSet.
#
# fabric.type: EFA turns on Elastic Fabric Adapter for the pool, so the gang's
# cross-node traffic and ModelExpress's peer-to-peer weight transfer run over an
# RDMA fabric. Without it multi-node NCCL falls back to TCP, which is slow and
# unstable.
apiVersion: modelplane.ai/v1alpha1
kind: InferenceCluster
metadata:
name: eks-us-east
labels:
modelplane.ai/region: us-east
spec:
stack: Dynamo
cluster:
source: EKS
eks:
region: us-east-1
nodePools:
- name: gpu-l4
className: l4-1x-g6-efa
nodeCount: 2
minNodeCount: 2
maxNodeCount: 2
zones:
- us-east-1b
fabric:
type: EFA
Provisioning the pool and installing the stack takes about 15 minutes:
kubectl wait --for=condition=Ready ic/eks-us-east --timeout=20mCache the weights
A gang reads its weights from a shared cache, so pods don’t each pull a copy. Create the namespace and the cache:
kubectl create namespace ml-team# The shared read-write-many cache the gang serves from, hydrated once from
# Hugging Face. Both gang pods mount it and read weights from it over EFS,
# instead of each pulling its own copy. Qwen2.5-14B is open, so it needs no
# token. Its FP16 weights are about 29 GB, so sizeGiB leaves headroom.
apiVersion: modelplane.ai/v1alpha1
kind: ModelCache
metadata:
name: qwen2-5-14b
namespace: ml-team
spec:
source: HuggingFace
huggingFace:
repo: Qwen/Qwen2.5-14B-Instruct
sizeGiB: 40
Deploy the gang
The Leader and Worker run the same vllm serve, differing only in node rank.
$(MODELPLANE_LEADER_ADDRESS) resolves to the leader on either stack, but
$(MODELPLANE_RANK) isn’t injected on Dynamo yet, so the worker derives its rank
from Grove’s GROVE_PCLQ_POD_INDEX.
Multi-node deployments
covers this. Both opt into ModelExpress with --load-format modelexpress, so the
worker pulls its weights from the leader over EFA rather than reading the cache
again.
# Qwen2.5-14B served across two L4 nodes as a gang. The FP16 weights (~29 GB)
# don't fit one L4's 23 GB, so the engine is a Leader + Worker gang,
# pipeline-parallel across two g6.8xlarge nodes with one L4 each. Both pods mount
# the shared ModelCache and claim an EFA interface for the fabric.
#
# The cluster runs the Dynamo stack, so Grove and the KAI Scheduler gang-schedule
# the two pods, and Modelplane composes them as a Grove PodCliqueSet.
# $(MODELPLANE_LEADER_ADDRESS) resolves to the leader on Dynamo, but
# $(MODELPLANE_RANK) isn't injected there yet (modelplaneai/modelplane#418), so
# each command sets its own --node-rank: 0 on the leader, and
# $$((GROVE_PCLQ_POD_INDEX + 1)) on the worker ($$ escapes past Kubernetes,
# leaving $((...)) for the shell to evaluate).
#
# Notes on the engine flags:
# --pipeline-parallel-size=2 splits the model across the two nodes;
# --tensor-parallel-size=1 keeps one GPU per node. Pipeline parallelism sends
# only activations between nodes, so it stays light on the fabric.
# --distributed-executor-backend=mp is vLLM's native multiprocessing multi-node
# path; vllm/vllm-openai:v0.23.0 no longer ships Ray.
# --load-format modelexpress loads weights through the ModelExpress server the
# Dynamo stack runs: the leader seeds from the cache and publishes itself, and
# the worker pulls peer-to-peer over EFA rather than reading the cache again.
# The vLLM image doesn't ship the loader, so pip install it first.
# --load-format=runai_streamer is the alternative that reads the cache
# directly, on any stack.
# --max-model-len=8192 caps context so the KV cache fits alongside the weights.
# FI_PROVIDER=efa points libfabric at the EFA interface; NCCL_DEBUG=INFO logs the
# transport NCCL picks, so you can confirm it's EFA and not TCP.
apiVersion: modelplane.ai/v1alpha1
kind: ModelDeployment
metadata:
name: qwen2-5-14b
namespace: ml-team
spec:
replicas: 1
template:
spec:
modelCacheRef:
name: qwen2-5-14b
engines:
- name: qwen
members:
- role: Leader
nodeSelector:
devices:
- name: gpu
count: 1
selectors:
- cel: |
device.capacity["gpu.nvidia.com"].memory.compareTo(quantity("20Gi")) >= 0
- name: efa
count: 1
selectors:
- cel: |
device.driver == "dra.net"
template:
spec:
containers:
- name: engine
image: vllm/vllm-openai:v0.23.0
env:
- name: FI_PROVIDER
value: "efa"
- name: NCCL_DEBUG
value: "INFO"
command:
- /bin/sh
- -c
- >-
pip install --index-url https://pypi.nvidia.com modelexpress &&
exec vllm serve Qwen/Qwen2.5-14B-Instruct
--served-model-name=qwen2.5-14b
--tensor-parallel-size=1
--pipeline-parallel-size=2
--distributed-executor-backend=mp
--nnodes=2 --node-rank=0
--master-addr=$(MODELPLANE_LEADER_ADDRESS)
--load-format modelexpress
--max-model-len=8192
--gpu-memory-utilization=0.90
--port=8000
- role: Worker
worker:
nodes: 1
nodeSelector:
devices:
- name: gpu
count: 1
selectors:
- cel: |
device.capacity["gpu.nvidia.com"].memory.compareTo(quantity("20Gi")) >= 0
- name: efa
count: 1
selectors:
- cel: |
device.driver == "dra.net"
template:
spec:
containers:
- name: engine
image: vllm/vllm-openai:v0.23.0
env:
- name: FI_PROVIDER
value: "efa"
- name: NCCL_DEBUG
value: "INFO"
command:
- /bin/sh
- -c
- >-
pip install --index-url https://pypi.nvidia.com modelexpress &&
exec vllm serve Qwen/Qwen2.5-14B-Instruct
--served-model-name=qwen2.5-14b
--tensor-parallel-size=1
--pipeline-parallel-size=2
--distributed-executor-backend=mp
--nnodes=2 --node-rank=$$((GROVE_PCLQ_POD_INDEX + 1))
--master-addr=$(MODELPLANE_LEADER_ADDRESS)
--headless
--load-format modelexpress
--max-model-len=8192
--gpu-memory-utilization=0.90
--port=8000
Wait until READY shows True. The first start hydrates the cache, so it’s
slower than later ones:
kubectl get md -n ml-team --watchOn the workload cluster the gang is a Grove PodCliqueSet, the Dynamo stack’s
multi-node workload in place of a LeaderWorkerSet:
kubectl get podcliquesets.grove.io -A # workload clusterExpose and query
# Exposes the gang as one OpenAI-compatible URL. Modelplane composes one
# ModelEndpoint per replica, labeled modelplane.ai/deployment: qwen2-5-14b, so
# this selector reaches it. Read the public address from status.address:
# kubectl get ms qwen2-5-14b -n ml-team -o jsonpath='{.status.address}'
apiVersion: modelplane.ai/v1alpha1
kind: ModelService
metadata:
name: qwen2-5-14b
namespace: ml-team
spec:
endpoints:
- selector:
matchLabels:
modelplane.ai/deployment: qwen2-5-14b
Read the endpoint’s address and send it a request. The model field is the
--served-model-name the deployment sets:
ADDRESS=$(kubectl get ms qwen2-5-14b -n ml-team -o jsonpath='{.status.address}')
kubectl run -i --rm curl-test \
--image=curlimages/curl \
--restart=Never \
--env="ADDRESS=$ADDRESS" \
-- sh -c 'curl -s "$ADDRESS/v1/chat/completions" \
-H "Content-Type: application/json" \
-d "{\"model\":\"qwen2.5-14b\",\"messages\":[{\"role\":\"user\",\"content\":\"What is Kubernetes in one sentence?\"}],\"max_tokens\":100}"'The request routes through the gateway to the leader, which serves the gang’s one endpoint.