GlusterFS is an open-source distributed file system originally developed by Gluster Inc. and later acquired by Red Hat. It aggregates storage across multiple servers into a single unified POSIX namespace, presenting the combined capacity as a shared file system accessible over the network. For over a decade, GlusterFS served as a common choice for organizations that needed distributed shared storage without a proprietary SAN, particularly for media files, backup targets, and shared home directories.
GlusterFS uses a distributed hash table (DHT) to distribute files across storage bricks, where a brick is a directory on a local file system within each storage node. The system’s translator stack handles replication, erasure coding, quorum, self-heal, and POSIX compliance in software layers stacked above the local file system. There is no metadata server: file placement is computed client-side from the DHT, which eliminates a single point of failure but also means the client must participate in placement decisions.
How GlusterFS Works
GlusterFS clusters are composed of trusted storage pools: a set of nodes (called peers) that have been joined together. Each peer contributes one or more bricks to the pool. Volumes are created by combining bricks according to a volume type:
- Distributed volumes spread files across bricks using DHT. No redundancy; a brick failure results in data loss.
- Replicated volumes write each file to multiple bricks simultaneously, providing fault tolerance. The typical configuration is 2x or 3x replication.
- Erasure-coded volumes (disperse volumes) distribute data and parity stripes across bricks, similar in concept to RAID-6, with lower storage overhead than full replication.
- Distributed-replicated volumes combine distribution across replica sets, the most common production configuration.
Client access is via FUSE (Filesystem in Userspace), NFS, or SMB. The FUSE client processes requests in userspace, which adds context-switch overhead on every I/O operation.
GlusterFS and Kubernetes: Where It Falls Short
GlusterFS was designed for large sequential file workloads accessed via a POSIX file system interface. Modern Kubernetes stateful workloads, particularly databases, generate small random I/O operations at high concurrency. Every database write passes through the FUSE layer, through the GlusterFS translator stack, and across the network to a brick. This path adds latency and overhead on every operation that a native block storage protocol eliminates.
The more immediate operational problem is the Kubernetes CSI driver. The kubernetes/gluster-csi-driver project has no active maintainers. It does not receive security patches, does not track Kubernetes API compatibility, and does not implement current CSI features such as volume snapshots or cloning. Teams running GlusterFS-backed persistent volumes on Kubernetes are using a CSI driver with no upstream maintenance path.
GlusterFS also does not natively support the block device semantics that KubeVirt virtual machines require. VM disks need a block device, not a POSIX file system. Accessing block storage through a file system layer adds overhead and does not support the access patterns VM operating systems generate.
🚀 Replacing GlusterFS with a maintained, block-native alternative? Simplyblock provides a Kubernetes CSI driver that is actively maintained, with native NVMe/TCP block storage and no FUSE overhead. 👉 See the GlusterFS alternative
Why Red Hat Moved Away from GlusterFS
Red Hat acquired Gluster Inc. in 2011 and integrated GlusterFS into its storage portfolio as Red Hat Gluster Storage (RHGS). For a period, GlusterFS was the default persistent storage recommendation for OpenShift Container Platform. Red Hat subsequently deprecated GlusterFS in favor of OpenShift Data Foundation (ODF), which uses Ceph as its storage engine. Red Hat Gluster Storage reached end of life, and the OpenShift ecosystem moved to CSI-native Ceph or alternative block storage solutions.
For teams still running GlusterFS-backed storage on Red Hat® OpenShift®, this transition means they are operating a storage layer that no longer has active development or a supported upgrade path from the platform vendor.
Split-Brain: The Operational Risk in Replicated GlusterFS
Replicated GlusterFS volumes are vulnerable to split-brain: a condition where nodes in a replica set disagree on the authoritative state of a file after a network partition or crash. GlusterFS includes a self-heal daemon that detects and repairs divergent copies, but split-brain events that the daemon cannot resolve automatically require manual intervention to identify the authoritative copy. In a database workload context, this is a serious operational risk.
Teams who have encountered GlusterFS split-brain in production typically describe the recovery process as fragile: identifying the correct copy, resolving the self-heal backlog, and verifying data integrity requires deep familiarity with GlusterFS internals that many Kubernetes platform teams do not maintain. See split-brain in distributed storage for a detailed explanation of the failure mode and how erasure-coded architectures avoid it.
How Simplyblock Replaces GlusterFS
Simplyblock addresses all three primary pain points teams encounter when operating GlusterFS on Kubernetes: the unmaintained CSI driver, the POSIX file system overhead on block workloads, and split-brain risk.
Simplyblock provides a maintained CSI driver for Kubernetes and OpenShift with full support for persistent volumes, volume snapshots, volume cloning, and live VM migration. The storage path is NVMe/TCP block-native: no FUSE layer, no POSIX translation overhead, no split-brain state to manage. Erasure coding provides the same fault tolerance as GlusterFS replication at significantly lower raw storage overhead.
For teams migrating from GlusterFS, simplyblock installs via Helm or OperatorHub without changing the Kubernetes storage API surface. Applications that were using GlusterFS-backed PVCs continue to use standard Kubernetes PersistentVolumeClaims, provisioned against a new StorageClass pointing to simplyblock rather than GlusterFS.
Related Terms
GlusterFS is one of several distributed storage systems teams evaluate when building persistent storage for Kubernetes.
- Split-Brain in Distributed Storage
- What Is Erasure Coding
- OpenShift Data Foundation
- What Is KubeVirt Storage
- Software-Defined Block Storage
Questions and Answers
Is the GlusterFS Kubernetes CSI driver still maintained?
No. The kubernetes/gluster-csi-driver project has no active maintainers and is not receiving updates. Teams running it face no security patches, no compatibility updates for new Kubernetes versions, and no upstream path for CSI feature development such as snapshots or cloning.
Why is GlusterFS a poor fit for database workloads on Kubernetes?
GlusterFS is a POSIX distributed file system optimized for large sequential reads and writes. Database workloads generate small, random I/O at high concurrency. Every I/O operation passes through the FUSE userspace layer and the GlusterFS translator stack, adding latency and CPU overhead that a native block storage protocol eliminates. The performance gap is most visible under random 4K I/O at high queue depths, which is exactly the workload pattern databases generate.
What replaced GlusterFS in the Red Hat and OpenShift ecosystem?
Red Hat replaced GlusterFS with OpenShift Data Foundation (ODF), which uses Ceph as its storage engine. ODF provides block, file, and object storage interfaces via the Rook-Ceph Operator. Teams looking for a lighter-weight alternative to ODF often evaluate simplyblock, which provides Kubernetes-native block storage with lower resource overhead and without the Ceph operational complexity ODF inherits.
Can GlusterFS handle split-brain automatically?
GlusterFS includes a self-heal daemon that can resolve some split-brain scenarios automatically, but not all. Split-brain events that the daemon cannot resolve require manual intervention: the operator must identify which copy of the file is authoritative, mark the other copies as stale, and trigger self-heal. In a Kubernetes environment where storage must be self-managing, this manual recovery requirement is a significant operational liability.
Does simplyblock support migration from GlusterFS without application downtime?
Simplyblock installs as a new StorageClass alongside an existing GlusterFS deployment. Data migration can be performed volume by volume using standard Kubernetes tools or backup-and-restore processes. Application downtime is scoped to individual volume migration operations rather than requiring a full cluster storage migration.