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. On a
Dynamo cluster Grove
and the KAI Scheduler gang-schedule the two pods together, Modelplane composes
them as a Grove PodCliqueSet, and NVIDIA ModelExpress serves their weights.
This is the getting started tour scaled to two
nodes: one larger model on a spec.stack: Dynamo cluster.
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. The InferenceCluster runs two of them and sets
spec.stack: Dynamo, so Modelplane installs Grove, the KAI Scheduler, and
ModelExpress on the cluster.
# EKS g6.8xlarge, one NVIDIA L4 per node. A single L4 can't hold the 14B model,
# so the gang spans two nodes. This node has enough memory to hold the weights as
# they load, and the 100 GB disk holds the vLLM image.
apiVersion: modelplane.ai/v1alpha1
kind: InferenceClass
metadata:
name: l4-1x-g6
spec:
description: "EKS g6.8xlarge, 1x NVIDIA L4"
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)
# 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, and ModelExpress, which serves cached weights to the
# gang and moves them between replicas peer-to-peer.
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
nodeCount: 2
minNodeCount: 2
maxNodeCount: 2
zones:
- us-east-1b
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 load with --load-format modelexpress, so they read the cached
weights through the Dynamo stack’s ModelExpress server.
# 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.
#
# 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 $((...)) for the shell to evaluate).
#
# Notes on the engine flags:
# --pipeline-parallel-size=2 splits the model across the two nodes;
# --tensor-parallel-size=1 keeps one GPU per node. Pipeline parallelism sends
# only activations between nodes, so it stays light on the network.
# --distributed-executor-backend=mp is vLLM's native multiprocessing multi-node
# path; vllm/vllm-openai:v0.23.0 no longer ships Ray.
# --load-format modelexpress loads weights through the ModelExpress server the
# Dynamo stack runs. The first replica seeds from the cache and publishes
# itself; later replicas pull their weights peer-to-peer from a replica that
# already has them. The vLLM image doesn't ship the loader, so pip install it
# first. --load-format=runai_streamer is the alternative that always reads the
# cache directly, on any stack.
# --max-model-len=8192 caps context so the KV cache fits alongside the weights.
apiVersion: modelplane.ai/v1alpha1
kind: ModelDeployment
metadata:
name: qwen2-5-14b
namespace: ml-team
spec:
replicas: 1
template:
spec:
modelCacheRef:
name: qwen2-5-14b
engines:
- name: qwen
members:
- role: Leader
nodeSelector:
devices:
- name: gpu
count: 1
selectors:
- cel: |
device.capacity["gpu.nvidia.com"].memory.compareTo(quantity("20Gi")) >= 0
template:
spec:
containers:
- name: engine
image: vllm/vllm-openai:v0.23.0
command:
- /bin/sh
- -c
- >-
pip install --index-url https://pypi.nvidia.com modelexpress &&
exec vllm serve Qwen/Qwen2.5-14B-Instruct
--served-model-name=qwen2.5-14b
--tensor-parallel-size=1
--pipeline-parallel-size=2
--distributed-executor-backend=mp
--nnodes=2 --node-rank=0
--master-addr=$(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
template:
spec:
containers:
- name: engine
image: vllm/vllm-openai:v0.23.0
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.
Scale out with peer-to-peer loading
Add a second replica and ModelExpress shows what it’s for. The first replica seeds its weights from the cache and publishes itself as a source; the second loads them straight from the first, peer-to-peer, rather than reading the cache again.
Each replica is a gang of two nodes, so a second replica needs two more nodes. Grow the pool to four, then scale the deployment:
kubectl patch ic/eks-us-east --type=json -p '[
{"op":"replace","path":"/spec/nodePools/0/nodeCount","value":4},
{"op":"replace","path":"/spec/nodePools/0/minNodeCount","value":4},
{"op":"replace","path":"/spec/nodePools/0/maxNodeCount","value":4}]'
kubectl patch md/qwen2-5-14b -n ml-team --type=merge -p '{"spec":{"replicas":2}}'Once the second gang starts, watch its leader load from the first over ModelExpress:
kubectl logs -n default -l modelplane.ai/clique-role=leader -c engine --tail=-1 \
| grep "source worker" # workload cluster
# [Worker 0] Trying source worker 63d91022 (266 tensors)