Unlike Hyper-V which uses a parent partition model, VMware ESXi operates as a Type-1 hypervisor running directly on hardware. The memory requirements differ significantly:

// Sample code to check memory usage in ESXi
esxcli system stats kernel get -d "System heap"

ESXi 7.0 and later versions typically require:

• Minimum: 4GB RAM for installation
• Recommended: 16GB RAM for production environments
• Additional 2-4GB per TB of host memory for system overhead

The exact overhead depends on configuration. Use this PowerCLI snippet to calculate:

Get-VMHost | Select Name,
@{N="PhysicalMemory(GB)";E={[math]::Round($_.MemoryTotalGB,2)}},
@{N="MemoryOverhead(GB)";E={[math]::Round(($_.ExtensionData.Hardware.MemorySize - $_.MemoryTotalGB)/1GB,2)}}

Special features increase memory needs:

# Enabling VSAN adds ~1GB overhead
esxcli system settings advanced set -o /VSAN/MemoryOverhead -i 1024

Additional overhead scenarios:

• vCenter integration: +500MB
• NSX: +2GB
• DRS/HAS: +200MB

For a host with 128GB RAM running 20 VMs:

Total RAM: 128GB
ESXi overhead: ~4GB (base) + 1.28GB (1%/TB) = 5.28GB
Feature overhead: 2.5GB (vSAN+vCenter+DRS)
Available for VMs: 128 - 8 = 120GB

Use this esxtop command to monitor in real-time:

esxtop -b -n 1 -d 5 > memory_stats.csv

Key metrics to watch:

• PMEM/MEMSZ: Service console memory
• VMKMEM/MEMSZ: VMkernel memory
• HEAP: System heap usage

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Unlike Hyper-V which runs on Windows Server and requires memory for the parent partition, ESXi is a Type-1 bare-metal hypervisor with different memory management architecture. The minimum RAM requirement for ESXi 8.0 is 4GB, but real-world production environments require significantly more.

ESXi memory usage consists of:

• Service Console: ~300MB (management interface)
• VMkernel: Base 2GB + 0.02% of physical RAM
• VM overhead: Additional ~100MB per VM (varies by vHW version)

For a host with 128GB RAM running 20 VMs:

# ESXi 8.0 memory calculation formula
base_memory = 2048 # MB
vmkernel_overhead = 0.0002 * (128 * 1024) # 0.02% of physical RAM
vm_overhead = 20 * 100 # MB
total_overhead = base_memory + vmkernel_overhead + vm_overhead

print(f"Total ESXi overhead: {total_overhead}MB ({total_overhead/1024:.2f}GB)")

Production environments should maintain:

• Minimum 8GB for ESXi alone
• 10-15% headroom for vSphere services (HA, DRS, etc.)
• Additional buffers for memory ballooning and swap

Use esxtop command to view real memory utilization:

esxtop -b -n 1 | grep -E "PMEM|MEM"

Key metrics to watch:

• PSHARE: Memory shared between VMs
• MCTLSZ: Memory reserved by VMkernel
• VMKMEM: Total VMkernel memory usage

1. Always allocate 8-10% of total RAM to ESXi (minimum 8GB)
2. For memory-constrained hosts, disable unnecessary services:

   esxcli system visorfs ramdisk set --size-min 0 --size-max 0

3. Enable Memory Compression for better utilization