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77_Bare_Metal_OpenStack_VMs_OpenStack_Nested

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DEPLOYMENT 77 — Bare Metal → OpenStack → VMs → OpenStack (Nested)

Deployment Stack Overlay

┌──────────────────────────────────────────────────┐
│             Workload (App/Process)             │
├──────────────────────────────────────────────────┤
│               OpenStack (Nested)               │
├──────────────────────────────────────────────────┤
│                      VMs                       │
├──────────────────────────────────────────────────┤
│                   OpenStack                    │
├──────────────────────────────────────────────────┤
│                   Bare Metal                   │
└──────────────────────────────────────────────────┘

Detailed System Infrastructure

┌─────────────────────────────────────────────────────────────────┐
│              L2 TENANT VMs (nested cloud)                       │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  Tenant L2 VMs (launched via inner OpenStack)            │   │
│  │  These are VMs running inside VMs inside OpenStack       │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│              INNER OPENSTACK (L1 — running inside L0 VMs)       │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  Inner OpenStack control plane (Nova, Neutron, Keystone) │   │
│  │  Runs inside L0 Nova VMs (nested KVM enabled)            │   │
│  │  Inner Nova → libvirt → nested KVM → L2 VMs             │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│              OUTER OPENSTACK L0 (bare metal cloud)              │
│  ┌──────────────────────────────────────────────────────────┐   │
│  │  L0 Nova (provisions L1 OpenStack infra VMs)             │   │
│  │  L0 Neutron (networking for L1 VMs)                      │   │
│  │  L0 VMs: inner-controller, inner-compute × N             │   │
│  │  All with nested KVM enabled (cpu_mode=host-passthrough) │   │
│  └──────────────────────────────────────────────────────────┘   │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│              L0 KVM COMPUTE NODES + LINUX KERNEL                │
│  kvm-intel.ko nested=1 │ libvirt cpu_mode=host-passthrough       │
└────────────────────────────┬────────────────────────────────────┘
                             │
┌────────────────────────────▼────────────────────────────────────┐
│                       BARE METAL                                │
│  CPU (large — nested overhead 40-70%) │ RAM (massive pool)     │
└─────────────────────────────────────────────────────────────────┘

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

OpenStack CI testing (testing OpenStack upgrades using nested OpenStack), development/lab environments, and cloud providers offering "private cloud in a cloud."

Pros

  • Test OpenStack without physical hardware
  • Isolated OpenStack environments per project/team
  • Useful for telco labs

Cons

  • Extreme overhead (three layers deep)
  • Very resource intensive
  • Slow I/O and networking at L2
  • Production use extremely rare
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