🐳 Introduction

Docker uses storage drivers to manage the image layers and the container writable layer, which together form the root filesystem of a container. Each storage driver comes with its own performance profile, compatibility, and operational characteristics.

Choosing the right storage driver affects:

• Disk performance
• Startup time
• Copy-on-write efficiency
• Snapshot and rollback capabilities
• Scalability

Let’s explore all the storage drivers Docker has supported — past and present — along with their benefits, limitations, and preferred use cases.

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🧱 What Are Docker Storage Drivers?

A Docker storage driver is a backend mechanism that implements Docker’s layered filesystem model:

• Image layers = read-only
• Container layer = writable
• Floating union filesystem = combined view via mount

Docker abstracts this using different drivers based on the host OS and storage type.

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📋 List of Docker Storage Drivers

Driver	Supported OS	Status	Type
overlay2	Linux	Recommended	Copy-on-write
overlay	Linux	Legacy	Copy-on-write
aufs	Linux	Deprecated	Copy-on-write
devicemapper	Linux	Deprecated	Block-based
btrfs	Linux	Niche	CoW filesystem
zfs	Linux	Niche	CoW filesystem
vfs	Linux	Internal/test	Full copy
overlayfs (containerd)	Linux	Latest	Snapshotter

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🔧 1. overlay2 (Preferred)

Type: Union filesystem on overlayfs
Availability: Linux Kernel >= 4.0
Status: Default and recommended driver

✔️ Pros:

• Fast startup
• Low overhead
• Modern and actively maintained
• Scales well with many layers
• Wide kernel support

❌ Cons:

• Struggles with heavy file delete/create operations
• Issues with certain kernel bugs (older distros)

📦 Use Cases:

• CI/CD, Kubernetes, Docker Swarm, general Linux workloads

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📦 2. overlay (Legacy)

Type: Earlier version of overlay2
Availability: Linux Kernel >= 3.18
Status: Deprecated in favor of overlay2

📍 Notes:

• Lower performance than overlay2 due to single-dir merge
• Only use on very old distros without overlay2 support

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🌀 3. aufs (Advanced Multi-Layered Unification FS)

Type: Union filesystem
Availability: Ubuntu before 18.10
Status: Deprecated

✔️ Pros:

• Original filesystem for Docker
• Supports many layers

❌ Cons:

• No longer maintained in kernel
• Replaced by overlay2

📦 Use Cases:

• Older Ubuntu systems, legacy infrastructure

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🧱 4. devicemapper

Type: Block-level driver (thin provisioning)
Availability: RedHat, CentOS
Status: Deprecated

✔️ Pros:

• Snapshot capability
• Useful for high-scale, block-device orchestration (back in the day)

❌ Cons:

• Hard to configure (loopback by default is slow)
• Poor performance compared to overlay2

📦 Use Cases:

• Legacy RHEL/CentOS installations

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🌳 5. btrfs

Type: CoW filesystem, subvolumes
Availability: Linux (with btrfs volume)
Status: Supported but niche

✔️ Pros:

• Snapshotting built-in
• Very efficient for layered FS
• Native features like deduplication

❌ Cons:

• btrfs can be unstable in some configurations
• Requires dedicated filesystem

📦 Use Cases:

• Environments that already use btrfs (e.g. SuSE)

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💿 6. zfs

Type: CoW filesystem
Availability: Linux & Solaris (ZFS installed)
Status: Supported but niche

✔️ Pros:

• Robust, enterprise-grade
• Snapshots, compression, deduplication

❌ Cons:

• More memory usage
• Not native to Linux kernel
• Not trivial to deploy

📦 Use Cases:

• Enterprise-grade persistent data handling

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🧪 7. vfs

Type: Copy full files/directories
Status: Not for production

✔️ Pros:

• Portable
• Very simple

❌ Cons:

• No layer sharing
• Extremely slow
• Consumes huge amounts of disk

📦 Use Cases:

• Only for testing, debugging, or when CoW is unsupported

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🆕 8. overlayfs (via containerd snapshotter)

Type: Snapshot-based storage via containerd
Availability: Docker 29+, containerd installs
Status: New default for fresh Docker installs

✔️ Pros:

• Efficient, modern, Kubernetes-aligned
• Compatible with lazy loading, OCI image standards

❌ Cons:

• Requires new tooling (ctr, nerdctl)
• Different layer paths under /var/lib/containerd/...

📦 Use Cases:

• Docker Engine v29+, Kubernetes nodes, containerd-managed runtimes

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🧭 How to Choose the Right Storage Driver

Environment	Recommended Driver
Modern Linux (kernel >= 4.0)	overlay2
Docker 29+ (fresh install)	containerd overlayfs snapshotter
Old Ubuntu kernels	aufs or overlay
Devices with btrfs or zfs pre-installed	btrfs or zfs
Embedded systems	vfs
Kubernetes	overlayfs (via containerd)

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🛠️ Check Which Storage Driver Is In Use

docker info | grep "Storage Driver"
Code language: JavaScript (javascript)

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⚙️ Advanced: Check Containerd Snapshot Layers

ctr -n moby snapshots ls
ls /var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/<id>/fs
Code language: JavaScript (javascript)

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📌 Conclusion

Docker Storage Drivers have evolved from layered union filesystems like AUFS to state-of-the-art containerd-backed snapshotters. Understanding which driver you’re running — and whether it’s optimized for your workload — is key to Docker stability and performance.

👉 For modern deployments, overlay2 (or containerd snapshotters in v29+) is the gold standard.

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