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+# 🖥️ Hypervisors and Virtualization Platforms
+
+## Hypervisor Types
+
+| Type | Description | Examples |
+|-----|-------|----------|
+| **Type 1** (bare-metal) | Runs directly on hardware | VMware ESXi, Microsoft Hyper-V, KVM, Xen |
+| **Type 2** (hosted) | Runs on top of host OS | VirtualBox, VMware Workstation, Parallels |
+
+## Platform Overview
+
+| Platform | Hypervisor | License | Note |
+|-----------|-----------|---------|----------|
+| **VMware vSphere** | ESXi | Proprietary (Subscription from 2024) | Market leader, wide adoption. After Broadcom acquisition (2023), switched to per-core subscription, perpetual license discontinued |
+| **Microsoft Hyper-V** | Hyper-V | Windows Server / standalone | Integration with Azure, SCVMM |
+| **Proxmox VE** | KVM + LXC | Open source | Debian-based, web UI, low cost |
+| **Red Hat OpenStack / oVirt** | KVM | Open source | Open alternative, complex |
+| **Nutanix AHV** | KVM (fork) | Part of Nutanix | Integrated HCI solution |
+| **XCP-ng / Xen Server** | Xen | Open source | Successor to Citrix Hypervisor |
+| **Oracle VM** | Xen | Proprietary | Oracle ecosystem |
+
+## Key Concepts
+
+- **VM — Virtual Machine** — full virtualization, own kernel
+- **Container** — shared host kernel, lighter (Docker, LXC)
+- **Paravirtualization** — guest OS knows it runs in a VM (better I/O performance)
+- **NUMA** — Non-Uniform Memory Access, CPU/memory allocation optimization (see [SERVER-HW.md](SERVER-HW.md#numa))
+- **Overcommit** — allocating more vCPU/RAM than physically available (ratio management)
+- **Live Migration** — moving a running VM between hosts (vSphere vMotion, Hyper-V Live Migration)
+- **HA (High Availability)** — VM restart on another host upon failure
+- **DRS / Load Balancing** — automatic VM distribution based on load
+
+## VMware vSphere
+
+### VMware licensing (post-Broadcom 2024+)
+
+Since 2024, VMware only sells subscription licenses; perpetual + SnS (Support & Subscription) have been discontinued.
+
+| Product | Metric | Price (indicative) | What it includes |
+|---------|---------|-------------------|-------------|
+| **vSphere Standard** | Per core (min 16 cores/CPU) | ~$140/core/year | ESXi, vCenter, vMotion, HA, DRS basic |
+| **vSphere Enterprise Plus** | Per core | ~$220/core/year | All above + DRS advanced, SIOC, NIOC, Big Data Extensions |
+| **vSphere Foundation** | Per core (bundle) | ~$350/core/year | vSphere Enterprise Plus + Aria Operations, Aria Operations for Logs, Aria Automation |
+| **VMware Cloud Foundation (VCF)** | Per core (bundle) | ~$700/core/year | vSphere + vSAN + NSX + Aria full suite. Required for vSAN and NSX from 2025 |
+| **vSAN** | Per core (only as part of VCF from 2025) | No longer standalone | Storage virtualization, dedup, compression, encryption |
+| **NSX** | Per core (only as part of VCF from 2025) | No longer standalone | SDN, micro-segmentation, firewall, load balancing |
+
+**Key changes after Broadcom acquisition**:
+- Discontinued perpetual license sales (May 2024)
+- Discontinued standalone products: vSAN and NSX can no longer be purchased standalone (only within VCF)
+- Desktop and ROBO variants cancelled (migrated to VCF)
+- Average cost increase: 2–5× compared to the previous model (depends on size and product mix)
+- **Impact**: Many customers are migrating to Proxmox VE, Nutanix AHV, or Hyper-V
+
+**Per-core calculation**:
+```text
+Server: 2× EPYC 9654 (96C each) = 192 cores
+  vSphere Standard: 192 × $140 = $26,880/year
+  VCF: 192 × $700 = $134,400/year (incl. vSAN and NSX)
+For comparison: previously perpetual + SnS ≈ $15,000 one-time + $3,000/year
+```
+
+### VMware Exit Strategy (post-Broadcom 2024+)
+
+#### Context
+
+After Broadcom's acquisition of VMware (completed November 2023), the virtualization market experienced the biggest upheaval in its history. Changes include:
+
+- **Discontinuation of perpetual licenses** (February 2024) — mandatory subscription model
+- **Forced bundling** — 8,000+ SKUs reduced to 4 bundles (VCF, VVF, vSphere Standard/Foundation)
+- **Minimum 72-core commitment** (from April 2025) — small servers can no longer be licensed economically
+- **20% late renewal penalty** — no tolerance
+- **Price increase of 150–1,500%** depending on size and product mix
+- **Standalone products discontinued** — vSAN and NSX only within VCF
+- **Collapse of the partner ecosystem** — from 4,500+ partners to ~300 Premier
+
+According to Foundry/CIO.com survey (2025): **56%** of organizations plan to reduce VMware usage, **71%** are actively looking for on-premise alternatives. Gartner predicts a loss of ~35% of workloads within 3 years.
+
+#### Three Strategies
+
+| Strategy | Description | Suitable for |
+|-----------|-------|------------|
+| **Stay** | Accept new pricing, renew VCF/VVF subscription | Large organizations with deep integration where migration costs more than new licenses |
+| **Reduce** | Reduce VMware footprint, migrate part of workloads to alternatives, optimize the rest | Medium and large enterprises with heterogeneous environments |
+| **Exit** | Complete migration to an alternative platform | SMEs, organizations facing 3–6× cost increases, greenfield projects |
+
+#### Target Platforms — Comparison
+
+| Criterion | Proxmox VE | Nutanix AHV | Microsoft Hyper-V | Red Hat OpenShift Virtualization |
+|-----------|-----------|-------------|-------------------|----------------------------------|
+| **Hypervisor** | KVM + LXC | KVM (fork) | Hyper-V | KVM (KubeVirt) |
+| **License** | Open source (free), support ~€500/host/year | Per node subscription (30–60% savings vs VCF) | Windows Server license (Standard/Datacenter) | OpenShift subscription (core-based) |
+| **Live Migration** | Live Migration (Proxmox 8+) | AHV Live Migration | Live Migration (SMB/RDMA) | KubeVirt (VMI live migration) |
+| **HA** | Proxmox HA (watchdog, fencing) | Built-in HA (Prism) | Hyper-V HA (WS Failover Cluster) | OpenShift HA (self-healing) |
+| **Storage** | ZFS, Ceph, LVM | AOS (hybrid/SSD, erasure coding) | S2D, CSV, ReFS | OCS, Ceph, LSO |
+| **Backup** | Proxmox Backup Server (free) | Native snapshot + DR | Windows Server Backup / Veeam | OpenShift APIs + OADP |
+| **Price (3 years, 3 hosts)** | $0 + support $1,500 | ~$45,000–60,000 | $0 (Hyper-V Server free) or Windows Server license | ~$90,000+ (OpenShift) |
+| **Price (3 years, 10 hosts)** | $0 + support $5,000 | ~$150,000–200,000 | Windows Server Datacenter for unlimited VMs | ~$300,000+ (OpenShift) |
+| **Migration difficulty** | Medium (VMDK → QCOW2, VirtIO drivers) | Low (Nutanix Move tool) | Medium (V2V converter, SCVMM) | High (Kubernetes learning curve) |
+| **Linux support** | Excellent (native KVM) | Excellent (KVM-based) | Good (LIS drivers) | Excellent (KVM + OpenShift) |
+| **Windows support** | Good (VirtIO drivers) | Excellent (ALAS drivers, svpd) | Excellent (native) | Good (KubeVirt + VirtIO) |
+| **GPU passthrough** | VFIO (excellent) | GPU passthrough | DDA (Direct Device Assignment) | VFIO + GPU Operator |
+
+#### Migration Tools
+
+| Tool | Source Platform | Target Platform | Method |
+|---------|-------------------|-------------------|--------|
+| **Proxmox VMware Import Wizard** | VMware ESXi | Proxmox VE | Web GUI import via NFS/ESXi API. Limitation: snapshots must be removed, UEFI not supported before Proxmox 8.1 |
+| **Nutanix Move** | VMware ESXi, Hyper-V | Nutanix AHV | Virtual appliance, automated migration with minimal downtime, UEFI support, can retain IP/MAC |
+| **Veeam Backup & Replication v12.2+** | VMware ESXi | Proxmox VE | Backup/restore via Veeam, hot migration, Proxmox support from v12.2 |
+| **StarWind V2V Converter** | VMware ESXi | Proxmox, Hyper-V, XCP-ng | Free GUI tool, VMDK → QCOW2/raw/VHDX, CLI support, hot migrations |
+| **virt-v2v** | VMware ESXi, Xen, Hyper-V | KVM (libvirt) | Open source CLI tool, disk + driver conversion (virtio), suitable for bulk migration |
+| **Windows Admin Center VM Conversion Extension** | VMware ESXi | Hyper-V | Microsoft WAC extension, free, GUI-based, bulk migration |
+| **Platform9 vJailbreak** | VMware ESXi | OpenStack / KVM | In-place migration (no swing gear), open source |
+
+#### TCO Comparison — Example: 3 hosts (2× 20C CPU), 50 VMs
+
+| Platform | Year 1 | 3 Years Total | Note |
+|-----------|--------|---------------|----------|
+| **VMware VVF** (1-year rate) | $22,800 | $68,400 | 120 cores × $190/core/year |
+| **VMware VCF** | $42,000 | $126,000 | 120 cores × $350/core/year |
+| **Proxmox VE** (support) | $1,500 | $4,500 | 3× €500/host/year |
+| **Nutanix AHV** (average) | ~$18,000 | ~$54,000 | Per node subscription, estimate |
+| **Hyper-V** (Windows Server Datacenter) | $12,400 | $37,200 | One-time license per core, without SA |
+| **Hyper-V** (Azure Stack HCI) | ~$7,200 | ~$21,600 | ~$10/core/month, 120 cores |
+
+**Real-world example from Spiceworks (2026)**: A user reports VMware Essentials+ increasing from $1,900/year to $14,000/year (VVF) — a 7.4× increase.
+
+#### Decision Framework
+
+```
+1. Audit VMware environment
+   ├─ Number of hosts, core count, utilization
+   ├─ Feature dependency (vSAN, NSX, SRM)
+   ├─ Workload profile (Windows vs Linux, DB, GPU)
+   └─ Hardware refresh cycle
+
+2. Calculate TCO for VMware renewal (3 years)
+   ├─ VVF vs VCF vs current model
+   └─ Include audit risk, late renewal penalty
+
+3. Select target platform (1-2 candidates)
+   ├─ Proxmox: lowest TCO, Linux-heavy shops
+   ├─ Nutanix: enterprise HCI, low migration difficulty
+   ├─ Hyper-V: Windows-centric, Azure hybrid
+   └─ OpenShift: Kubernetes-first, platform engineering
+
+4. Plan migration phases
+   ├─ Wave 1: non-critical (dev/test, 1-2 months)
+   ├─ Wave 2: standard production (3-6 months)
+   ├─ Wave 3: mission-critical (6-12 months)
+   └─ Coexistence: VMware + target running in parallel
+
+5. Allow 18-48 months for complete exit (Gartner)
+```
+
+#### Real-World Case Studies
+
+| Organization | Starting Point | Target | Scale | Result |
+|-----------|---------|-----|--------|----------|
+| **Stanford University** | VMware (60+ nodes) | Proxmox VE (6 clusters) | 1,500 VMs | Completed 2025, increased automation, lower costs |
+| **Michelin** | VMware | Platform9 + OpenStack | Dozens of nodes | Platform engineering team, production workload migration |
+| **Czech enterprise (50-100 servers)** | VMware | Proxmox VE | ~100 VMs | Annual savings of ~340,000–500,000 CZK on licenses |
+
+#### Timing — Key Deadlines
+
+| Event | Date | Impact |
+|---------|-------|-------|
+| **Discontinuation of perpetual licenses** | February 2024 | Already done |
+| **72-core minimum** | April 2025 | Small server licensing became more expensive |
+| **vSphere 7 EOS** | April 2025 | Upgrade to 8.x required |
+| **ESXi 8.0 EOS** | October 2027 | Last supported version, migration deadline |
+| **Windows Server 2025 Hyper-V** | December 2025 | 64-host cluster, 2,048 vCPU per VM |
+| **Proxmox VE 9 + Datacenter Manager** | 2026 | Enterprise features, vCenter alternative |
+
+#### Recommendations
+
+| Scenario | Action |
+|--------|------|
+| **Small company (< 10 hosts), Linux workloads** | Migrate to Proxmox VE — immediate 100% license savings |
+| **Medium company (10-50 hosts), mixed workloads** | Evaluate Nutanix AHV (easy migration) or Proxmox (lower TCO) |
+| **Enterprise (50+ hosts), deep VMware integration** | Reduce strategy: optimize existing VMware + migrate selected workloads to OpenShift / Hyper-V |
+| **Microsoft shop** | Hyper-V / Azure Stack HCI — native Azure hybrid, no additional hypervisor licenses |
+| **Kubernetes-native team** | OpenShift Virtualization / KubeVirt — unify VM and container management |
+| **MSP / hosting provider** | Nutanix or OpenStack — multi-tenancy, vCloud Director alternative |
+
+#### Cluster Design
+
+- **Max cluster size**: 64 hosts (vSphere 8/9), 96 hosts (vSphere 8 + enhanced)
+- **Datastore limits**: max 256 datastores per host, max 65 TB per VMFS-6 datastore
+- **vSAN ready capacity**: recommended max 60–64 hosts per vSAN cluster
+- **Fault domains** — cluster division into host groups (rack awareness), min 3 fault domains for stretched cluster
+- **Admission control** — resource reservation for HA failover:
+  - **Host failures cluster tolerates** — most common (1–4 hosts)
+  - **Percentage of cluster resources** — reserve % of CPU/memory
+  - **Dedicated failover hosts** — dedicated host(s) for HA
+- **Cluster limits (vSphere 8/9)**:
+  - 960 VMs per host (vSphere 9 max)
+  - 15,000 VMs per cluster (vCenter max)
+  - 300 hosts per cluster (vSphere 8/9, hardware vMotion)
+
+### Microsoft Hyper-V Licensing
+
+| Variant | Metric | Price | What it includes |
+|----------|---------|------|-------------|
+| **Windows Server Standard** | Per core (min 16 licenses/server) + CAL | ~$1,000/core (one-time) + $200/CAL | 2 VM licenses (each with full Windows Server license) |
+| **Windows Server Datacenter** | Per core (min 16 licenses/server) + CAL | ~$6,200/core (one-time) + $200/CAL | Unlimited VMs, Storage Spaces Direct, Shielded VMs |
+| **Azure Stack HCI** | Per core (monthly) | ~$10–20/core/month (Azure hybrid benefit) | Hyper-V + S2D + Azure management, part of Azure subscription |
+| **Hyper-V Server** | Free | $0 | Standalone hypervisor (no management, no GUI, limited support) — no longer distributed as of 2025 |
+
+**Important**:
+- Windows Server Standard = 2 VMs per license. If you need 3 VMs on a 2-socket server, you need 2× Standard license (4 VMs) or Datacenter
+- **Azure Hybrid Benefit** — if you have Windows Server with SA (Software Assurance), you can use licenses in Azure at no additional cost
+- **CAL (Client Access License)** — every user or device accessing Windows Server must have a CAL (except Azure Hybrid Benefit)
+
+## Microsoft Hyper-V
+
+| Feature | Hyper-V | Note |
+|-----------|---------|----------|
+| **Max hosts per cluster** | 64 (Windows Server 2025) | Shared Nothing Live Migration |
+| **Max VMs per host** | 1,024 (WS 2022+) | Generation 2 VMs |
+| **Max vCPU per VM** | 240 (WS 2022+) | 64-host cluster |
+| **Max RAM per VM** | 12 TB (WS 2022+) | Dynamic memory |
+| **Live Migration** | SMB, CSV, RDMA | Compressed or RDMA |
+| **Storage** | CSV (Cluster Shared Volumes), ReFS | S2D for HCI |
+| **Nested Virtualization** | Yes | Intel VT-x / AMD-V |
+| **SCVMM** | System Center VMM | Enterprise management, fabric, P2V |
+
+### Hyper-V vs VMware Comparison
+
+| Feature | VMware vSphere | Microsoft Hyper-V |
+|-----------|---------------|-------------------|
+| **OS** | VMware ESXi (VMkernel) | Windows Server / Hyper-V Server |
+| **License** | Per CPU (subscription) | Windows Server license / Datacenter |
+| **Storage** | VMFS, NFS, vSAN, HCI | NTFS, ReFS, SMB, S2D |
+| **Live Migration** | vMotion (cross-vSwitch, long distance) | Live Migration (SMB/RDMA) |
+| **Storage Migration** | Storage vMotion (online) | Shared Nothing (data disk) |
+| **Replication** | vSphere Replication | Hyper-V Replica (ASR) |
+| **Management** | vCenter, vSphere Client | SCVMM, Hyper-V Manager, Admin Center |
+| **Linux support** | Excellent (open-vm-tools) | Good (Linux Integration Services) |
+| **TCO** | Higher | Lower (with Windows license) |
+
+## KVM
+
+### Architecture
+
+```
+Hardware ──> QEMU (I/O emulation) + KVM (kernel module, virtualization)
+                │
+           libvirt (API + management)
+                │
+        ┌───────┼───────────┐
+  virt-manager  virsh    openstack/proxmox
+```
+
+### Tuning
+
+- **CPU pinning** — `virsh vcpupin vm1 0 2` (vCPU 0 → physical core 2), prevents context switching
+- **Huge pages** — 2 MB / 1 GB pages instead of 4 KB, reduces TLB misses (VMs with large RAM): `echo 2048 > /proc/sys/vm/nr_hugepages`
+- **NUMA affinity** — VM pinned to one NUMA node (minimizes cross-NUMA memory access)
+  - `numactl --cpunodebind=0 --membind=0`
+  - `virsh numatune vm1 --nodeset 0`
+- **VirtIO** — paravirtualized I/O (virtio-net, virtio-blk, virtio-scsi) for better performance
+- **IO threads** — dedicated threads for QEMU I/O emulation
+
+### KVM Tuning Checklist
+
+- Verify HW virtualization: `lscpu | grep Virtualization`
+- Load KVM modules: `kvm`, `kvm_intel`/`kvm_amd`, `vfio-pci`
+- Optimize storage: raw/LVM (avoid qcow2 for performance workloads)
+
+## Storage in Hypervisors
+
+See also: [STORAGE.md](STORAGE.md) — detailed overview of storage protocols and configurations.
+
+| Type | Description | Protocols |
+|-----|-------|-----------|
+| **Local storage** | Disks directly in the server | SATA, SAS, NVMe |
+| **Shared storage** | SAN / NAS accessible to all hosts | Fibre Channel, iSCSI, NFS, SMB |
+| **vSAN / HCI** | Hyperconverged storage (server disks = single pool) | VMware vSAN, Nutanix, StarWind |
+| **Software-Defined** | SDS separates storage software from hardware | Ceph, GlusterFS, MinIO |
+
+## HCI Details
+
+| Feature | Nutanix (AOS + AHV) | VMware vSAN | Azure Stack HCI |
+|-----------|--------------------|-------------|----------------|
+| **Hypervisor** | AHV (KVM fork), ESXi optional | ESXi (required) | Hyper-V |
+| **Min. nodes** | 3 | 2 (witness) | 2 (witness) |
+| **Max nodes** | 80+ | 64 | 16 (typical) |
+| **Replication** | 2 or 3 copies + erasure coding | Mirroring (RAID 1), erasure coding | Mirroring + parity |
+| **Deduplication** | Cluster-level (post-process) | Disk-level (capacity tier) | ReFS (real-time) |
+| **Compression** | Inline (AOS 6+) | Dedup + compression combined | ReFS |
+| **Management** | Prism (web UI) | vCenter + vSAN UI | Windows Admin Center |
+| **Licensing** | Per node subscription | Per CPU subscription | Per core subscription |
+| **Ecosystem** | Built-in DR, backup, security | Broad ISV ecosystem | Azure integration |
+| **Use case** | Enterprise VDI, general VM | VMware-centric shops | Azure hybrid, branch offices |
+
+## Virtualization Platforms — Comparison
+
+| Capability | VMware vSphere | Microsoft Hyper-V | Proxmox VE | Nutanix AHV |
+|-----------|---------------|-------------------|------------|-------------|
+| Live Migration | vMotion | Live Migration | Live Migration | Live Migration |
+| HA | vSphere HA | Hyper-V HA | Proxmox HA | Built-in |
+| DRS/balancing | DRS | SCVMM / AKS | HA groups | Built-in |
+| Storage vMotion | yes | when VM is off | ZFS send/recv | Built-in |
+| Snapshots | yes | yes | yes | yes |
+| Backup API | CBT (Changed Block Tracking) | Hyper-V WMI / RCT | Proxmox Backup Server | Native |
+| GPU passthrough | vGPU (NVIDIA Grid) | DDA | VFIO passthrough | GPU passthrough |
+| Licensing | Per CPU / subscription | Windows Server license | Open source (free) | Per node subscription |
+
+## OpenStack
+
+- **Distributions**: Red Hat OpenStack, Canonical Charmed OpenStack
+- **Services**: Nova (compute), Cinder (block), Neutron (networking), Glance (images), Swift (object)
+- **Use case**: Telco, large private clouds, MNO (MANO, NFVI)
+- **Complexity**: High — complex deployment and maintenance
+
+---
+
+## Variant Hypervisor Configurations by Size and Storage Type
+
+### Platform Selection by Use Case
+
+| Use Case | Primary Choice | Alternative | Rationale |
+|----------|---------------|-------------|------------|
+| **VMware shop, enterprise** | vSphere 8/9 | Hyper-V | Most comprehensive ecosystem, vSAN, SRM, broadest ISV support |
+| **Microsoft shop, Azure hybrid** | Hyper-V / Azure Stack HCI | vSphere | Windows Server CAL already in place, S2D, Azure Arc, native Hyper-V Replica |
+| **SME / low budget** | Proxmox VE | XCP-ng / Hyper-V (free) | Open source, built-in Ceph, ZFS, PBS, no license costs |
+| **HCI greenfield** | Nutanix AHV | VMware vSAN | All-in-one, simple management, built-in DR and backup |
+| **Hyperscale / telco** | OpenStack (RHOSP) | — | Multi-tenancy, NFVI, MANO, Neutron SDN, Ceph integration |
+
+### Variant A: Small Deployment (2-3 hosts, local storage)
+
+For small companies, branch offices, edge, dev/test. No shared storage — HA provided at the application level or via VM replication.
+
+| Parameter | Proxmox VE | VMware vSphere | Hyper-V |
+|----------|-----------|---------------|---------|
+| **CPU** | 1× EPYC 9124-9224 / Xeon 4410Y (8-16C) | 1× EPYC 9124-9224 / Xeon 4410Y | 1× Xeon 4410Y / EPYC 9124 |
+| **RAM** | 64-128 GB (DDR5-4800, 1DPC) | 64-128 GB | 64-128 GB |
+| **OS disk** | 2× SATA SSD RAID1 (240-480 GB) | 2× SATA SSD RAID1 | 2× SATA SSD RAID1 |
+| **VM storage** | ZFS RAID10 (4-6× NVMe/SATA SSD) | VMFS local (4-6× SSD RAID5/10) | ReFS CSV (4-6× SSD RAID10) |
+| **Network** | 2× 10/25 GbE LACP | 2× 10/25 GbE LACP + management | 2× 10/25 GbE LACP |
+| **Management** | Proxmox web UI (1× node) | vCSA / vCenter (1× appliance) | Windows Admin Center / SCVMM |
+| **HA** | Proxmox HA (watchdog, fencing) | vSphere HA (1 host failure) | Hyper-V HA (WS Failover Cluster) |
+| **Backup** | Proxmox Backup Server | Veeam B&R (Community) | Windows Server Backup / Veeam |
+| **License** | Free (support ~€500/host/year) | vSphere Essentials (~$600/3 hosts) | Windows Server Standard (2 VMs) |
+
+**Use case**: Startup, branch office, dev/test, < 200 VMs, no SAN, minimal budget.
+
+**Advantages**: Low cost, simple management. **Disadvantages**: Limited scalability, host failure = VM unavailability.
+
+### Variant B: Medium HCI (3-6 hosts, vSAN / Ceph)
+
+Hyperconverged infrastructure — storage runs on the same hosts as VMs.
+
+| Parameter | VMware vSAN | Proxmox + Ceph | Nutanix AHV |
+|----------|------------|----------------|-------------|
+| **CPU** | 1-2× EPYC 9334-9654 (16-32C) | 1-2× EPYC 9224-9334 (12-24C) | 1-2× EPYC 9334-9654 |
+| **RAM** | 256-512 GB | 128-256 GB | 256-512 GB |
+| **Cache tier** | 1-2× NVMe cache (write buffer) | — (Ceph uses RAM/OSD) | 1-2× NVMe (oplog) |
+| **Capacity tier** | 4-8× SSD (SAS/SATA) | 4-8× HBA NVMe/SSD (OSD) | 4-6× SSD (extent store) |
+| **Network** | 4× 25 GbE (vSAN + VM + mgmt) | 4× 25 GbE (Ceph public + cluster) | 4× 25 GbE (storage + VM) |
+| **Fault domain** | Rack awareness (3 racks min) | CRUSH rack level | Rack awareness |
+| **Replication** | RAID-1 mirroring (FTT=1) | 3× replication / EC 8+3 | 2× copies + EC |
+| **Dedupe/Compress** | Dedup + compression (capacity) | ZFS / Ceph compression (inline) | Inline compression |
+| **HA limit** | 1-3 host failures | 1-2 host failures (replication) | 1-2 host failures |
+| **Min. hosts** | 2 + witness | 3 (MON + OSD) | 3 |
+
+**Use case**: Medium company, VDI, general virtualization, 50-500 VMs.
+
+**Recommendation**: For vSAN → min. 4 hosts for FTT=1 with erasure coding. For Ceph → min. 3 hosts, ideally 5+, each OSD host = 1 OSD per NVMe for maximum IOPS.
+
+### Variant C: Enterprise FC SAN (6+ hosts)
+
+Classic 3-tier architecture — compute (hosts) + storage (SAN) + network separated.
+
+| Parameter | VMware vSphere | Hyper-V |
+|----------|---------------|---------|
+| **CPU** | 2× EPYC 9654-9965 (32-64C) | 2× EPYC 9654-9965 / Xeon 8592+ |
+| **RAM** | 512-2048 GB (DDR5) | 512-2048 GB |
+| **OS disk** | 2× SATA SSD RAID1 (480 GB) | 2× SATA SSD RAID1 |
+| **Storage** | FC SAN LUN (2× FC HBA 32/64G) | FC SAN LUN or CSV over SMB |
+| **App network** | 2-4× 25/100 GbE LACP | 2-4× 25/100 GbE LACP |
+| **Storage network** | 2× FC 32/64G (multipath) | 2× FC 32/64G or SMB Multichannel |
+| **vMotion / Live Migration** | 2× 25 GbE dedicated (vMotion) | 2× 25 GbE dedicated (SMB/RDMA) |
+| **Management** | vCenter (VCSA), NSX, Aria | SCVMM, Azure Arc |
+| **Cluster max** | 64-96 hosts (vSphere 8/9) | 64 hosts (WS 2025) |
+| **Admission control** | 1-4 host failures | Nodes reserve |
+| **DRS / Balancing** | DRS (fully automated) | SCVMM / AKS load balancing |
+
+**Use case**: Enterprise, databases, critical applications, 500-5000 VMs.
+
+**Storage variants**: FC SAN (lowest latency), iSCSI (lower CAPEX), NFS (simpler management).
+
+**FC SAN topology**:
+```
+                 ┌─────────────────────────────────────┐
+                 │              FC Fabric              │
+                 │   ┌─────────┐       ┌─────────┐    │
+                 │   │ Switch 1│       │ Switch 2│    │
+                 │   └────┬────┘       └────┬────┘    │
+                 └────────┼─────────────────┼──────────┘
+                    ┌─────┴─────┐     ┌─────┴─────┐
+               ┌───┤ FC HBA 1  ├─┐ ┌─┤ FC HBA 2  ├───┐
+               │   └───────────┘ │ │ └───────────┘   │
+            ┌──┴──┐          ┌──┴──┴──┐          ┌──┴──┐
+            │Host1│          │Host2   │          │Host3│ ...
+            └─────┘          └────────┘          └─────┘
+```
+
+### Variant D: Hyperscale OpenStack (20+ hosts)
+
+For telco, large private clouds, MANO/NFVI environments.
+
+| Parameter | Red Hat OpenStack | Canonical Charmed OpenStack |
+|----------|-------------------|-----------------------------|
+| **Compute** | Nova + KVM | Nova + KVM |
+| **Storage** | Ceph (Cinder/RBD) + Swift | Ceph + Swift |
+| **Network** | Neutron + OVN/OVS + DPDK | Neutron + OVN/OVS |
+| **CPU per host** | 2× EPYC 9654-9965 (64-128C) | 2× EPYC 9654-9965 |
+| **RAM per host** | 512-1024 GB | 512-1024 GB |
+| **Storage per host** | Ceph OSD (4-12× NVMe/SSD) | Ceph OSD |
+| **Network per host** | 4-8× 100 GbE (DPDK/VPP) | 4× 100 GbE |
+| **Control plane** | 3-9× control node (HA) | 3-7× control node |
+| **Orchestration** | TripleO / OpenStack Kolla | Juju + charms |
+| **SDN** | OVN, OpenDaylight | OVN |
+| **NFVI ready** | Yes (SR-IOV, NUMA, huge pages) | Yes |
+| **Min. size** | 9 nodes (3 ctl + 3 compute + 3 ceph) | 7 nodes |
+
+**Use case**: Telco (5G UPF, MNO), hyperscale private cloud, > 5000 VMs.
+
+### Connectivity Summary by Platform
+
+| Platform | App / VM Network | Storage Network | Replication / HA | Management |
+|-----------|-------------|-------------|----------------|------------|
+| **Proxmox small** | 2× 10/25 GbE LACP | — (local ZFS) | — | 1× 1 GbE |
+| **vSAN (3-6)** | 2× 25 GbE LACP | 2× 25 GbE (vSAN) | vSAN traffic | 1× 1 GbE |
+| **Proxmox Ceph (3-6)** | 2× 25 GbE | 2× 25 GbE (Ceph public) | 2× 25 GbE (Ceph cluster) | 1× 1 GbE |
+| **Nutanix (3-6)** | 2× 25 GbE | Dedicated storage VLAN | Replication traffic | 1× 1 GbE |
+| **vSphere FC SAN (6+)** | 2-4× 25/100 GbE LACP | 2× FC 32/64G multipath | 2× 25 GbE (vMotion) | 1× 1 GbE + SAN mgmt |
+| **Hyper-V FC SAN (6+)** | 2-4× 25/100 GbE LACP | 2× FC 32/64G or SMB | 2× 25 GbE (Live Migration) | 1× 1 GbE |
+| **OpenStack (20+)** | 2-4× 100 GbE | 2× 100 GbE (Ceph) | 2× 100 GbE (OVN) | 1× 1 GbE |
+
+## Resources
+
+Links, books and standards: [sources/infrastructure/sources.md](sources/infrastructure/sources.md)
+
+### Recommended Reading
+
+| Book | Authors | ISBN | Description |
+|-------|--------|------|-------|
+| Virtualization Essentials (3rd ed., 2023) | Matthew Portnoy | 978-1119481513 | Practical guide to virtualization: from hypervisor basics (Type 1/Type 2), VM configuration (CPU, memory, storage, networking) to cloud computing and DevOps. "Learning-by-doing" approach with tutorials. Author is a Senior System Engineer at VMware/Splunk. |
+| VMware vSphere Design (2nd ed.) | Guthrie, Lowe, Coleman | 978-1119130312 | Comprehensive guide to vSphere infrastructure design: hardware selection, network layout, security, storage and hypervisors. Describes a framework for design, decision analysis and best practices from experienced VMware architects. |
+
+*Last revision: 2026-06-04*