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60_Bare_Metal_GlusterFS_KVM_Shared-Storage_VMs

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DEPLOYMENT 60 — Bare Metal → GlusterFS + KVM → Shared-Storage VMs

Deployment Stack Overlay

┌──────────────────────────────────────────────────┐
│             Workload (App/Process)             │
├──────────────────────────────────────────────────┤
│               Shared-Storage VMs               │
├──────────────────────────────────────────────────┤
│                GlusterFS + KVM                 │
├──────────────────────────────────────────────────┤
│                   Bare Metal                   │
└──────────────────────────────────────────────────┘

Detailed System Infrastructure

┌─────────────────────────────────────────────────────────────────┐
│              VIRTUAL MACHINES (live-migratable)                 │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  VM A (libvirt KVM)    VM B    VM C                      │   │
│  │  disk: qcow2 file on GlusterFS mount                     │   │
│  │  live migration → same qcow2 file accessible from both   │   │
│  │                   KVM hosts via GlusterFS                │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│              KVM HYPERVISOR HOSTS                               │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  Host 1 (KVM)               Host 2 (KVM)                 │   │
│  │  libvirt                    libvirt                       │   │
│  │  GlusterFS client (FUSE)    GlusterFS client (FUSE)      │   │
│  │  mount: /mnt/vms            mount: /mnt/vms              │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │  FUSE or native GlusterFS mount
┌────────────────────────────▼────────────────────────────────────┐
│              GLUSTERFS CLUSTER                                  │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  GlusterFS Trusted Pool                                  │   │
│  │  ┌────────────────────────────────────────────────────┐  │   │
│  │  │  Brick 1 (storage node 1: /data/gluster/vm-vol)    │  │   │
│  │  │  Brick 2 (storage node 2: /data/gluster/vm-vol)    │  │   │
│  │  │  Volume type: Replicated (2-way or 3-way mirror)   │  │   │
│  │  └────────────────────────────────────────────────────┘  │   │
│  │  glusterd (daemon on each storage node)                  │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│                       BARE METAL                                │
│  KVM hosts: CPU│RAM│Local SSD (for OS) │ 10GbE NIC             │
│  Storage nodes: CPU│RAM│HDDs or SSDs│10GbE NIC                 │
│  (can be converged: KVM hosts also serve as GlusterFS bricks)  │
└─────────────────────────────────────────────────────────────────┘

Technical Implementation Details

  • Isolation: Hardware-assisted virtualization (VT-x/AMD-V).
  • Storage: Virtual disks (qcow2/vmdk) on shared or local storage.
  • Management: Orchestrated via native CLI or high-level API controllers.

Use Case

Small to medium deployments wanting shared storage for KVM VM live migration without Ceph complexity or a SAN investment. Used in SMBs and research environments.

Pros

  • Simpler than Ceph for small deployments
  • Enables KVM live migration
  • No specialized storage hardware needed
  • POSIX filesystem interface

Cons

  • GlusterFS reliability issues at scale historically
  • Red Hat has reduced GlusterFS investment
  • Performance not competitive with Ceph at scale
  • Split-brain risk without proper quorum config
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