If you're running:

• CI/CD pipelines


• Batch jobs


• Video transcoding


• ETL pipelines


• AI preprocessing

You do not need persistent storage.

In fact, persistent volumes can:

• Increase cost


• Add lifecycle complexity


• Leak unused PVCs


• Slow down I/O

Instead, Kubernetes offers ephemeral storage primitives that are:

✅ Fast

✅ Auto-cleaned

✅ Zero long-term storage cost

✅ Perfect for temporary workloads

This tutorial walks through a full working lab.

🧠 What Is Ephemeral Storage?

Ephemeral storage is storage that:

• Exists only for the lifetime of a Pod


• Is automatically deleted when the Pod is removed


• Lives on node-local disk or memory

No manual cleanup.

No orphaned volumes.

No storage bills after the job completes.

🧰 What You’ll Learn

We’ll demonstrate:

1️⃣ emptyDir (disk-backed)

2️⃣ emptyDir (memory-backed)

3️⃣ Generic Ephemeral Volumes (dynamic PVC lifecycle)

4️⃣ Automatic cleanup behavior

1️⃣ Disk-Backed emptyDir

emptyDir is the simplest ephemeral storage mechanism.

It:

• Is created when the Pod starts


• Lives as long as the Pod runs


• Is deleted when the Pod is deleted

Example

apiVersion: v1

kind: Pod

metadata:

  name: emptydir-disk

spec:

  containers:

  - name: writer

    image: busybox

    command: ["/bin/sh", "-c"]

    args:

      - |

        dd if=/dev/zero of=/scratch/test.img bs=1M count=100

        sleep 600

    volumeMounts:

    - mountPath: /scratch

      name: scratch

  volumes:

  - name: scratch

    emptyDir: {}

What Happens

• A 100MB file is created inside /scratch
  


• The data lives on node-local disk


• Delete the Pod → data disappears

💡 Perfect for CI build artifacts or temporary data transforms.

2️⃣ Memory-Backed emptyDir (Ultra Fast)

You can mount emptyDir into RAM using medium: Memory.

volumes:

- name: memvol

  emptyDir:

    medium: Memory

This creates a tmpfs mount.

Why It’s Powerful

• Extremely fast


• Zero disk I/O


• Perfect for caching or scratch processing

⚠ Important:

It counts against container memory limits.

If memory is exceeded → Pod may be evicted.

3️⃣ Generic Ephemeral Volumes (Dynamic PVC)

This is where things get powerful.

Kubernetes can dynamically create a PVC that:

• Is scoped to a Pod


• Is automatically deleted when the Pod is deleted


• Uses your StorageClass

Example

volumes:

- name: eph

  ephemeral:

    volumeClaimTemplate:

      spec:

        accessModes: ["ReadWriteOnce"]

        resources:

          requests:

            storage: 1Gi

When the Pod starts:

• Kubernetes creates a PVC


• A backing volume is provisioned

When the Pod is deleted:

• The PVC is deleted automatically


• The storage is released

✔ No PVC leaks

✔ No manual cleanup

Perfect for:

• Data processing jobs


• ML training scratch space


• Large temporary workloads

🔥 What We Verified in the Lab

⚖ Before vs After Using Ephemeral

❌ Traditional Approach (Persistent Volumes Everywhere)

• PVC lifecycle management required


• Risk of leaked volumes


• Network storage latency


• Ongoing storage cost

✅ Ephemeral Strategy

• Faster local I/O


• Automatic cleanup


• No lifecycle overhead


• Lower cloud cost


• Better autoscaling behavior

🏗 Real-World Architecture Patterns

CI/CD Build Cluster

1. Job starts


2. Repo cloned into emptyDir
   


3. Build artifacts generated


4. Image pushed


5. Pod exits


6. Storage auto-deleted

Zero leftovers.

Video Transcoding System

1. Download file


2. Process locally


3. Upload output


4. Pod terminates

Scratch space disappears automatically.

ETL / Data Transformation

1. Download dataset


2. Transform locally


3. Upload results


4. Storage wiped

No persistent cost.

☁ Cloud Optimization (Advanced)

On managed Kubernetes like:

• Microsoft Azure (AKS)


• Amazon Web Services (EKS)


• Google Cloud (GKE)

You can combine ephemeral volumes with:

• Local SSD nodes


• Ephemeral OS disks


• Autoscaling node pools

This produces:

⚡ Extremely fast build clusters

💰 Reduced storage cost

🔄 Clean horizontal scaling

🚨 Best Practices

✔ Always set ephemeral-storage resource requests/limits

✔ Monitor node disk pressure

✔ Use separate node pools for build workloads

✔ Avoid storing logs in emptyDir (use log shipping)

✔ Use memory-backed volumes only when needed

🎯 When NOT to Use Ephemeral Storage

Avoid ephemeral storage if:

• Data must survive Pod restart


• You need shared access across Pods


• You need backups or snapshots

Use PersistentVolumes in those cases.

🧩 Final Takeaway

Ephemeral storage is one of the most underused performance optimizations in Kubernetes.

For temporary workloads, it gives you:

• Speed


• Simplicity


• Cost efficiency


• Automatic cleanup

If you’re building:

• CI/CD infrastructure


• Batch processing platforms


• Media pipelines


• AI preprocessing clusters

Ephemeral storage should be your default choice.