Storage Translation

Storage Translation

You translate the storage layer: StorageClasses, PVCs, PVs, and the data movement plan for each stateful workload. You do not move data yourself — that's data-migration. You produce the design, the StorageClass set, and the per-PVC handoff.

Purpose

Map every EBS / EFS / FSx volume and every StorageClass to a GKE equivalent and produce the snapshot or live-replication plan that data-migration will execute.

When to use this skill

• Phase 3, after gke-landing-zone.
• The user asks to "translate storage", "convert StorageClasses", "plan stateful workload migration".

Prerequisites

• 01-discovery/inventory.json storage section (PVs, PVCs, StorageClasses, EBS volumes, EFS file systems).
• Target GKE clusters from 03-landing-zone.

Procedure

Step 1 — Translate StorageClasses

For each source StorageClass:

Sample translated StorageClass:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: gp3-encrypted
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: pd.csi.storage.gke.io
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
reclaimPolicy: Delete
parameters:
  type: pd-balanced
  disk-encryption-kms-key: projects/data-prod/locations/us-central1/keyRings/portage/cryptoKeys/disk
  csi.storage.k8s.io/fstype: ext4

Always set volumeBindingMode: WaitForFirstConsumer — it prevents pods from being scheduled to a zone where their PD doesn't exist.

Step 2 — Per-PVC migration plan

For each PVC in inventory.json:

Capture:

• Owning workload (StatefulSet / Deployment).
• Current size, access modes, current usage.
• Underlying volume type (EBS gp3 / io2 / EFS / FSx).
• Snapshot capability (already snapshotted? interval?).
• RPO/RTO targets from the readiness report.

Produce a per-PVC plan with one of these strategies:

Strategy A — Cold migration via backup tool (Velero)

Best for: workloads with an acceptable downtime window, no replication tooling, simple snapshot/restore semantics.

# On EKS
velero backup create payments-pvc-${TS} \
  --include-namespaces payments \
  --include-resources persistentvolumes,persistentvolumeclaims \
  --selector app=payments

# Mirror backup bucket to GCS
gcloud storage cp -r s3://velero-prod gs://portage-velero-prod

# On GKE
velero restore create payments-pvc-${TS} \
  --from-backup payments-pvc-${TS} \
  --namespace-mappings payments:payments

Velero's CSI snapshotter cannot directly translate EBS → PD. Use the data-mover pattern: Velero packages PV contents into the object store, restore re-creates a PD-backed PV with the same data.

Strategy B — Block-level replication (pre-cutover sync)

Best for: high-volume workloads where downtime is small and copy time is large.

1. Create the target PV+PVC on GKE pinned to a temporary "shadow" pod with dd/rsync/pgpv-replication-class tooling.
2. Initial sync: copy from EKS-side snapshot (exported to object storage as image) into the GKE PD via a one-shot Job.
3. Incremental sync: depends on workload (database WAL shipping, application-level replication).
4. At cutover: stop EKS workload, do final delta sync, mount to the target StatefulSet.

Produce per-workload Job manifests for the sync.

Strategy C — Application-native replication

Best for: databases. PostgreSQL streaming replication, MySQL binlog replication, MongoDB replica set additions, Redis replicas. The "PVC" in that case never literally moves; the data does.

This crosses into data-migration. storage-translation simply notes "Strategy C — handled by data-migration" for these PVCs and links to the data-migration plan.

Strategy D — Object-storage-fronted (re-platform)

Best for: workloads that could use object storage but happen to use a PVC for caching. Replace the PVC with a gcsfuse-mounted bucket via the GCS Fuse CSI driver. This is a re-platform decision and surfaces as an escalation.

Strategy E — RWX (multi-pod read-write)

Best for: workloads using EFS access points across many pods.

• Identify per-AP usage patterns and pod counts.
• Map to Filestore Enterprise (recommended) or NetApp Volumes (when you need NetApp APIs).
• For very high IOPS / many-pod scale-out, evaluate Parallelstore.
• Produce a migration plan: provision Filestore, copy contents via gcsfuse intermediate or DataSync (cross-cloud), cut over.

Step 3 — Snapshot, retention, and DR

For each migrated PVC:

1. Plan a VolumeSnapshotClass and snapshot schedule on GKE matching the existing EKS schedule.
2. Verify CMEK encryption parity. If EKS volumes were encrypted with a KMS key, the GKE PVs use the equivalent Cloud KMS key declared in the StorageClass.
3. Plan cross-region DR if the EKS workload had cross-region snapshot copying — use Backup for GKE for application-level backups including PVCs.

Step 4 — Validate sizing

GKE Persistent Disks have minimum sizes (e.g., pd-balanced minimum 10 GiB; performance scales with size). If a source PVC is smaller than the GKE minimum, request the user's confirmation before bumping size. Do not silently change sizes.

Step 5 — Stateful workload pre-cutover dry-run

For at least one representative stateful workload per class (DB, queue, file share):

1. Stand up a non-prod copy of the workload on GKE with the translated StorageClass and a small PV.
2. Restore a recent snapshot.
3. Run the workload's smoke tests.
4. Capture the timing: snapshot copy, restore, mount-to-ready latency.

This timing feeds traffic-cutover's window calculation.

Step 6 — Output

07-storage-translation/
├── storage-design.md
├── manifests/
│   ├── storageclasses/
│   ├── volumesnapshotclasses/
│   └── filestores/             # Filestore instance manifests where applicable
├── pvc-plans/
│   └── <namespace>-<pvc>.md    # Per-PVC strategy and runbook
├── terraform/
│   └── filestore.tf            # Filestore / Parallelstore as TF where appropriate
└── escalations.md

Decision points

Outputs / Deliverables

07-storage-translation/
├── storage-design.md
├── manifests/
├── pvc-plans/
├── terraform/
└── escalations.md

Validation

• Every PVC in inventory.json has a pvc-plans/<ns>-<pvc>.md entry with a strategy.
• Every StorageClass referenced by any translated workload exists in manifests/storageclasses/.
• Provisioning a test PVC on GKE with the new StorageClass succeeds and produces a PV in the expected zone.
• volumeBindingMode: WaitForFirstConsumer on every translated SC.
• Snapshot/restore round-trip works for a representative PVC of each class.

Escalation triggers

• PVC backed by storage with no clean GKE equivalent (FSx OpenZFS, certain Storage Gateway flavors).
• RWX usage that exceeds Filestore tier limits even at Enterprise.
• Workload with no acceptable downtime AND no application-native replication path. Surface; the user must choose between extending the cutover window, accepting downtime, or re-platforming.
• Volumes encrypted with externally-managed keys (e.g., HSM-backed KMS) where the GCP target uses CMEK with Cloud HSM and key import is not yet planned.

Common pitfalls

• Treating gp2 as pd-standard. It's not — gp2 is SSD. Use pd-balanced.
• Forgetting volumeBindingMode. Default Immediate causes PV provisioning at PVC creation time, often in the wrong zone.
• Snapshot semantics. EBS snapshots are incremental and account-scoped. PD snapshots are also incremental, but you can't directly import an EBS snapshot — you copy data.
• EFS performance modes. EFS Bursting → Filestore Basic; EFS Provisioned/Max IO → Filestore Enterprise or Parallelstore.
• Quorum on stateful clusters. When migrating Kafka, etcd, MongoDB, do not try to live-extend the quorum across clusters across clouds. Build a new quorum on GKE, replicate data, switch consumers.
• Freshly provisioned PDs ship with a lost+found directory that crashes Kafka log scanning. Mount via subPath for Kafka-class workloads. See LFF-33.
• Stuck PVs at decommission time are a known class of CSI finalizer race. Verify finalizer cleanup before destroying any source cluster. See LFF-32.

References

• Canonical sources: reference/sources.md.
• Persistent Disk types.
• Hyperdisk overview.
• Filestore tiers.
• Parallelstore.
• Backup for GKE.
• Best practices for stateful applications on GKE.
• Velero — cold-migration tool.
• data-migration — runs the actual data move.
• docs/glossary.md — storage service map.