Google Cloud Storage Fuse

GKE Training Deployment (Fit-Gated, Tuned Mount)

Provision a performance-tuned gcsfuse mount for training workloads whose code is hardcoded to POSIX paths (run the SKILL.md fit gate first). GKE version gates are noted inline.

Decision table: pick the mount mechanism

Never pass profile:aiml-* as a mount option yourself on GKE: Cloud Storage FUSE CSI volumes do not support the profile field or --profile option on any volume type (ephemeral or PV/PVC). The pre-installed StorageClasses are the only supported way to use profiles on GKE; on older clusters, set the profile's individual options explicitly instead (manifest B).

Never use the legacy Workload Identity flow (Google service account + roles/iam.workloadIdentityUser + iam.gke.io/gcp-service-account KSA annotation). The current flow is a direct principal:// IAM binding on the bucket — no GSA, no JSON keys (step 2).

Step 1 — Verify cluster gates

CLOUDSDK_METRICS_ENVIRONMENT="gcs-skills gcs-skills/1.0 (skill:google-cloud-storage-fuse)" \
    gcloud container clusters describe CLUSTER --location=LOCATION \
    --format="value(currentMasterVersion, addonsConfig.gcsFuseCsiDriverConfig.enabled, workloadIdentityConfig.workloadPool)"

Requirements: GcsFuseCsiDriver addon enabled, a Workload Identity pool set, and the cluster version against these gates:

Check node cache media (drives step 4):

kubectl describe node NODE_NAME | grep "cloud.google.com/gke-ephemeral-storage-local-ssd"

Step 2 — Authentication: direct principal:// binding

Grant the workload's Kubernetes ServiceAccount access on the bucket directly. Use roles/storage.objectViewer for read-only training data; roles/storage.objectUser if the workload also writes.

CLOUDSDK_METRICS_ENVIRONMENT="gcs-skills gcs-skills/1.0 (skill:google-cloud-storage-fuse)" \
    gcloud storage buckets add-iam-policy-binding gs://BUCKET \
    --member="principal://iam.googleapis.com/projects/PROJECT_NUMBER/locations/global/workloadIdentityPools/PROJECT_ID.svc.id.goog/subject/ns/NAMESPACE/sa/KSA_NAME" \
    --role="roles/storage.objectViewer"

The KSA itself is a plain ServiceAccount with no annotations (manifest A).

For cross-project mounts (GKE cluster in Project A, bucket in Project B): GKE's storage profile controller attempts an upfront bucket scan using the GKE control-plane service agent (service-PROJECT_A_NUM@container-engine-robot.iam.gserviceaccount.com). To prevent Pods getting stuck in SchedulingGated (gke-gcsfuse/bucket-scan-pending) with 403 Forbidden, either set skipCSIBucketAccessCheck: "true" on the PV (Manifests A & B) to skip the control-plane pre-scan, or grant roles/storage.bucketViewer and roles/storage.objectViewer to the cluster's GKE service agent on Project B's bucket. The Step 2 principal:// binding likewise goes on the bucket in Project B, not in the cluster project: the member string still references Project A's Workload Identity pool (PROJECT_NUMBER and PROJECT_ID are the cluster project's), but the IAM policy must be granted in the bucket-owning project.

Step 3 — What the training profile does (and does not do)

The gcsfusecsi-training StorageClass layers two things:

• Client profile aiml-training sets: implicit-dirs, metadata-cache: negative-ttl-secs: 0, metadata-cache: ttl-secs: -1, metadata-cache: stat-cache-max-size-mb: -1. It does not enable the file cache — no client profile does.

• GKE CSI automation (StorageClass parameters) adds: gcsfuseMetadataPrefetchOnMount: "true", skipCSIBucketAccessCheck: "true", and dynamic file-cache sizing — the driver picks cache capacity and medium from node resources, bucket size, and sidecar limits (fuseFileCacheMediumPriority: "gpu:ram|lssd,tpu:ram,general_purpose:ram|lssd", memory budget 0.7 of allocatable, ephemeral-storage budget 0.85). So on the profile path the file cache is auto-enabled and auto-sized — verify it actually engaged (step 6), because the driver silently disables it when no medium has enough space.

List the pre-installed classes: kubectl get sc -l gke-gcsfuse/profile=true (gcsfusecsi-training, gcsfusecsi-checkpointing, gcsfusecsi-serving).

To tune or customize mount options on the PV:

• Scope massive namespaces (10M+ files): Add mountOptions: ["only-dir=<subfolder>"] (or config only-dir: <subfolder>) to restrict FUSE tracking to the active dataset partition (e.g. train/). This avoids populating stat cache entries for the full namespace (~1.5 GiB RAM per 1M files) and accelerates directory traversal.

• Override profile defaults: Set spec.mountOptions or spec.csi.volumeAttributes on the PV. If you set file-cache: max-size-mb manually, dynamic sizing is overridden for that component and you must also configure a custom read cache volume (gke-gcsfuse-cache).

Step 4 — File cache on the manual path (older clusters)

For multi-epoch training that re-reads the dataset, the file cache is the single highest-impact knob; without the profile automation you must enable and size it explicitly:

• Size file-cache: max-size-mb (or the fileCacheCapacity volume attribute) to hold the working dataset.

• Media, in order of preference: Local SSD (A3/GPU nodes with the cloud.google.com/gke-ephemeral-storage-local-ssd: "true" label; A3+ is set up automatically), RAM disk for TPU v6+ nodes, pd-ssd/ pd-balanced otherwise. Avoid the boot disk.

• The cache lands on the sidecar's emptyDir by default, so the pod annotation gke-gcsfuse/ephemeral-storage-limit must exceed the cache capacity.

Step 5 — Manifests

Every pod consuming a gcsfuse volume requires the sidecar-injection annotation gke-gcsfuse/volumes: "true" — PV/PVC and ephemeral volumes alike.

Sidecar sizing and resource limits:

• gke-gcsfuse/ephemeral-storage-limit: Must exceed the file cache capacity when using emptyDir.

• gke-gcsfuse/cpu-limit and gke-gcsfuse/memory-limit: Leave unset (or "0", the default on GKE ≥ 1.29.1-gke.1670000). Setting conservative CPU limits causes aggressive CFS throttling during multi-threaded prefetching; setting tight memory limits causes the sidecar to be OOMKilled (ExitCode 137) when stat cache or streaming buffers fill. If limits are mandated, size memory well above the combined stat cache (~1.5 GiB / 1M files) and streaming block budget.

Manifest A — KSA + profile-path PV/PVC (GKE ≥ 1.35.1-gke.1616000):

# ksa.yaml - no GSA annotation; access comes from the principal:// binding
apiVersion: v1
kind: ServiceAccount
metadata:
  name: KSA_NAME
  namespace: NAMESPACE
---
# pv.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: training-data-pv
spec:
  storageClassName: gcsfusecsi-training
  capacity:
    storage: 1Ti          # placeholder; not enforced for gcsfuse
  accessModes:
    - ReadOnlyMany
  mountOptions:
    - ro                  # training data is read-only for the pods
  csi:
    driver: gcsfuse.csi.storage.gke.io
    volumeHandle: BUCKET  # the bucket name
    volumeAttributes:
      skipCSIBucketAccessCheck: "true"  # prevents SchedulingGated 403 on cross-project mounts
---
# pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: training-data-pvc
  namespace: NAMESPACE
spec:
  storageClassName: gcsfusecsi-training
  volumeName: training-data-pv
  accessModes:
    - ReadOnlyMany
  resources:
    requests:
      storage: 1Ti

Manifest B — older clusters: replicate the profile as explicit options. Same PV/PVC as above, but storageClassName: "" and:

  mountOptions:
    - ro
    - implicit-dirs
    - metadata-cache:negative-ttl-secs:0
    - metadata-cache:ttl-secs:-1
    - metadata-cache:stat-cache-max-size-mb:-1
    - file-cache:max-size-mb:512000        # size to the dataset
    - file-cache:cache-file-for-range-read:true
    # - only-dir=data/train                # optional: scope namespace to save stat-cache RAM
  csi:
    driver: gcsfuse.csi.storage.gke.io
    volumeHandle: BUCKET
    volumeAttributes:
      gcsfuseMetadataPrefetchOnMount: "true"   # GKE ≥ 1.32.1-gke.1357001
      skipCSIBucketAccessCheck: "true"         # prevents SchedulingGated 403 on cross-project mounts

The infinite metadata TTL and unlimited stat cache assume the dataset is immutable during training; budget ~1.5 GiB RAM per million files for the stat cache.

Manifest C — training Job:

apiVersion: batch/v1
kind: Job
metadata:
  name: training-job
  namespace: NAMESPACE
spec:
  template:
    metadata:
      annotations:
        gke-gcsfuse/volumes: "true"              # required for sidecar injection
        gke-gcsfuse/ephemeral-storage-limit: 600Gi   # > file cache capacity
        # gke-gcsfuse/cpu-limit: "0"             # default unlimited; do not set tight limits
        # gke-gcsfuse/memory-limit: "0"          # default unlimited; avoid OOMKill (Exit 137)
    spec:
      serviceAccountName: KSA_NAME
      nodeSelector:
        cloud.google.com/gke-ephemeral-storage-local-ssd: "true"
      containers:
        - name: trainer
          image: TRAINING_IMAGE
          volumeMounts:
            - name: training-data
              mountPath: /data
              readOnly: true
      volumes:
        - name: training-data
          persistentVolumeClaim:
            claimName: training-data-pvc
      restartPolicy: Never

Step 6 — Apply and verify

kubectl apply -f ksa.yaml -f pv.yaml -f pvc.yaml -f training-job.yaml
kubectl exec POD -c trainer -- ls /data | head    # mount works, data visible

Then confirm the cache engaged and troubleshoot common blockers:

• SchedulingGated (gke-gcsfuse/bucket-scan-pending): Upfront bucket access check failed (common on cross-project mounts). Fix by setting skipCSIBucketAccessCheck: "true" in spec.csi.volumeAttributes or granting bucketViewer/objectViewer to the cluster's GKE service agent.

• Sidecar OOMKilled (ExitCode 137) / CPU throttling: Sidecar limits throttled prefetching or ran out of memory under stat/file cache load. Remove gke-gcsfuse/cpu-limit and gke-gcsfuse/memory-limit (or set "0").

• Profile cache verification: Check the GCSFuseCSIRecommendation log entry for the decision block (fileCacheBytes, fileCacheMedium); the warning "No suitable file cache medium found" means the cache was silently disabled — fix node media or sidecar limits.

• After the first epoch, read gcsfusecsi/file_cache_read_count in Cloud Monitoring (exported by default on GKE ≥ 1.33.0-gke.2248000; disable via the disableMetrics: "true" volume attribute): hits should approach 100% of reads from epoch 2 onward. For the full diagnosis workflow and metric map, see Performance & Cost Diagnosis.

Non-GKE variants

Documentation

• GKE profiles for Cloud Storage FUSE

• CSI driver setup and Workload Identity

• Static PV/PVC provisioning

• Sidecar configuration

• CSI performance tuning

• Volume attributes reference

• Profile-based configurations