Proxmox VE (Virtual Environment) is a powerful open-source virtualization platform that supports KVM-based virtual machines and LXC containers. One of the critical decisions in a Proxmox deployment is selecting the right storage backend. Two of the most powerful options available natively in Proxmox are Ceph and ZFS. Both offer advanced features, but they serve different needs.
This article explores the differences, strengths, weaknesses, and best use cases for Ceph and ZFS in a Proxmox environment.
What is Ceph?
Ceph is a distributed, software-defined storage system that provides object, block, and file storage in a unified platform. In Proxmox, Ceph is primarily used to provide RBD (RADOS Block Device) storage that appears as shared, highly available block storage for VMs and containers.
Key Features of Ceph:
- Shared block storage across multiple nodes
- Built-in replication and fault tolerance
- Horizontal scalability (scale by adding more nodes/disks)
- Native integration with Proxmox GUI
- Works well with 10GbE+ networking
What is ZFS?
ZFS is a combined file system and volume manager that offers high performance, data integrity, and ease of use. ZFS runs on a single node and is excellent for managing direct-attached storage with features like snapshots, compression, and deduplication.
Key Features of ZFS:
- Built-in software RAID (mirroring, RAIDZ)
- Data integrity via checksumming and scrubbing
- Instant snapshots and clones
- Native support in Proxmox (used for VM disk images)
- Ideal for local or node-based storage
Feature Comparison
Feature | Ceph | ZFS |
|---|---|---|
| Storage Type | Distributed, shared | Local file system |
| Best Use Case | Multi-node clusters, HA | Single node or small clusters |
| Data Redundancy | Replication or erasure coding | RAIDZ, mirrors |
| Networking | Requires high-speed (10GbE+) | Not required |
| Performance | Scales with cluster size; network adds latency | High IOPS on local storage |
| Ease of Setup | Complex (needs at least 3 nodes) | Simple (even on a single node) |
| Maintenance | Requires knowledge of Ceph commands and health | Easier with built-in tools |
| Snapshots/Clones | Supported, but limited control in GUI | Fully supported |
| Self-healing | Yes, automatic rebalancing | Yes, via scrubs and checksums |
| Live Migration | Seamless (shared storage) | Requires replication or shared storage |
| Backup Integration | Works with PBS; offloading may be needed | Easily integrates with ZFS send/receive |
Deployment Considerations
Cluster Size
- Ceph requires at least 3 nodes with multiple OSDs to be useful. Ideal for larger deployments with 5+ nodes.
- ZFS works well with 1–3 nodes, especially when storage is local to the host.
Complexity
- Ceph demands more initial configuration and ongoing monitoring, including OSD health, MON quorum, placement groups, and CRUSH maps.
- ZFS is much simpler to manage, with most tasks manageable through the Proxmox GUI.
Disk Usage Efficiency
- Ceph with replication (e.g., 3x) has lower usable capacity. For example, 3TB raw capacity yields 1TB usable with 3x replication.
- ZFS RAIDZ2 offers better efficiency (~66% usable with 6 disks), but no distribution across nodes.
Performance
- ZFS on SSD or NVMe is blazing fast for single-node performance.
- Ceph has more overhead due to network and replication but scales well and performs well with SSD-backed OSDs and fast interconnects.
Use Case Examples
Small Cluster (2–3 Nodes)
- Recommended: ZFS with Proxmox Replication
- Why: Shared storage via Ceph is overkill; ZFS with replication can handle failover.
Enterprise Cluster (3+ Nodes, High Uptime Required)
- Recommended: Ceph
- Why: High availability, shared storage for live migration, scalability.
Scalable Infrastructure (Cloud-Like)
- Recommended: Ceph
- Why: Easy to add more storage or compute nodes, supports massive scale.
Hybrid Strategy
You can also combine ZFS and Ceph in some scenarios:
- Use Ceph for shared VM storage across the cluster.
- Use ZFS locally on each node for backup targets, scratch space, or dedicated workloads (like databases that benefit from local IOPS).
- Proxmox Backup Server (PBS) also benefits from ZFS on the backup node due to fast snapshotting and ZFS send/receive.
Which Should You Choose?
Use Case | Best Choice |
|---|---|
| Single-node setup | ZFS |
| Simple 2-node cluster | ZFS with Proxmox replication |
| HA, multi-node cluster | Ceph |
| Need shared storage & migration | Ceph |
| High IOPS from local storage | ZFS |
| Limited admin resources | ZFS |
| Horizontal scalability needed | Ceph |
In summary:
- Choose Ceph if you’re building a resilient, high-availability cluster with shared storage needs.
- Choose ZFS if you’re looking for performance, simplicity, and data integrity on single or small clusters.