Storage

CobaltCore's storage layer is built on Ceph, a distributed storage system that delivers block, file, and object storage from a single unified cluster. The surrounding components handle Kubernetes-native lifecycle management, high-availability quorum in stretched clusters, object replication, and dynamic storage allocation.

Architecture

The storage stack is organized into three layers:

Foundation - Ceph provides the core distributed storage engine. All other components either operate it, extend it, or observe it.

Operations - Rook manages the full Ceph cluster lifecycle as a Kubernetes operator. Arbiter extends quorum into stretched topologies by deploying external monitors at a tiebreaker site.

Data Services - Chorus provides zero-downtime S3/Swift object replication and migration. Liquid-Ceph enables dynamic, on-demand storage allocation.

Components

Component	Layer	Role
Ceph	Foundation	Distributed storage engine - block (RBD), file (CephFS), object (RGW)
Rook	Operations	Kubernetes operator for Ceph lifecycle management
Arbiter	Operations	External Ceph monitors for quorum in stretched clusters
Chorus	Data Services	Zero-downtime object storage replication and migration
Liquid-Ceph	Data Services	Dynamic storage allocation across the Ceph cluster

Storage interfaces

Interface	Use case
RBD (RADOS Block Device)	VM disks, database volumes - thin-provisioned, snapshotted block storage
CephFS	Shared POSIX filesystem for workloads that need file access across multiple VMs
RGW (RADOS Gateway)	S3 and Swift-compatible object storage for application data

Data flow

Applications / VMs
        │
┌───────┴────────────────────┐
│  RBD  │  CephFS  │  RGW    │  ← Ceph interfaces
└───────┴────────────────────┘
        │
    RADOS (distributed object store)
        │
   OSDs across cluster nodes
        │
   ┌────┴─────┐
   │  Rook    │  ← manages daemon lifecycle via Kubernetes CRDs
   └──────────┘
        │
   ┌────┴──────┐   ┌─────────┐   ┌────────────┐
   │  Arbiter  │   │  Chorus │   │ Liquid-Ceph│
   └───────────┘   └─────────┘   └────────────┘
   (quorum)        (replication)  (allocation)

High availability

Ceph achieves HA through monitor quorum (3 or 5 monitors), OSD replication or erasure coding, and MDS standby daemons. In stretched deployments spanning two sites, Arbiter deploys a third monitor at a tiebreaker site to maintain quorum if one site goes offline.

See also

• Observability - Prometheus metrics, Perses dashboards, and Prysm for the storage stack
• Ceph upstream architecture docs
• Rook documentation