When dealing with Windows failover clusters in VMware environments, the VMXNET3 adapter's receive buffer configuration directly impacts both network performance and host memory utilization. The two key parameters are:

Small Rx Buffers: Default 512 (range 128-4096)
Rx Ring #1 Size: Default 1024 (range 512-4096)

The relationship between buffers and ring size follows this pattern:

Total Buffer Memory = (Small Rx Buffers * 2KB) + (Rx Ring #1 * 64B)

For example, with default settings:

(512 * 2048) + (1024 * 64) = 1,114,112 bytes (~1.06MB per vNIC)

The memory comes from two distinct sources:

• Guest OS: Ring buffers consume non-paged pool memory
• ESXi Host: Packet buffers allocate from host physical memory

For a cluster node experiencing packet drops, consider this PowerShell script to adjust settings:

# Query current settings
Get-NetAdapterAdvancedProperty -Name "vEthernet*" -DisplayName "Small Rx Buffers","Rx Ring #1"

# Set optimized values (example for 16GB RAM VM)
Set-NetAdapterAdvancedProperty -Name "vEthernet0" -DisplayName "Small Rx Buffers" -DisplayValue 2048
Set-NetAdapterAdvancedProperty -Name "vEthernet0" -DisplayName "Rx Ring #1" -DisplayValue 2048

Implement this performance counter check to validate your changes:

# Check for packet drops post-configuration
Get-Counter '\Network Interface(*)\Packets Received Discarded' -SampleInterval 5 -MaxSamples 12 |
    Select-Object -ExpandProperty CounterSamples |
    Where-Object {$_.CookedValue -gt 0}

Key operational factors to monitor:

• Non-paged pool usage in guests (check via Performance Monitor)
• Host memory ballooning indicators
• Network latency metrics during cluster sync operations

For a 4-node cluster showing intermittent node evictions:

# Typical investigation workflow:
1. Check cluster logs for "NETFT" events
2. Verify VMXNET3 buffer stats via esxtop (network view)
3. Compare with physical NIC metrics on ESXi hosts
4. Validate MTU consistency across all paths

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When configuring VMXNET3 network adapters in VMware environments, particularly for Windows failover clusters, buffer sizing becomes critical. The interplay between Small Rx Buffers and Rx Ring #1 directly impacts both network performance and host memory utilization.

The receive buffers and ring size work in tandem:

// Conceptual representation in driver code
typedef struct {
    uint32_t small_rx_buffers;  // Default 512
    uint32_t rx_ring1_size;     // Default 1024
    void* buffer_pool;          // Memory allocation
} vmxnet3_config;

Each buffer consumes 2KB (default size), meaning:

• 512 buffers → ~1MB memory usage
• 2048 buffers → ~4MB memory usage

Use this PowerShell snippet to audit current settings:

Get-NetAdapterAdvancedProperty -Name "*" -DisplayName "Small Rx Buffers","Rx Ring #1" |
Select-Object -Property Name,DisplayName,DisplayValue |
Format-Table -AutoSize

Memory consumption formula:

Total Memory (MB) = (Small Rx Buffers × 2KB + Rx Ring #1 × 2KB) / 1024

The memory comes from non-paged pool in Windows guests. Monitor with:

typeperf "\Memory\Pool Nonpaged Bytes" -si 5 -sc 60

Critical thresholds:

• Windows Server 2016+: ~80% of non-paged pool triggers warnings
• Each VMXNET3 adapter at max settings (2048 buffers) uses ~8MB

Recommended registry settings for critical cluster nodes:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e972-e325-11ce-bfc1-08002be10318}\0001]
"SmallRxBuffers"=dword:00000800  ; 2048 buffers
"RxRing1"=dword:00000800        ; 2048 ring size

In our production environment with 150 VMs:

Setting	Before	After	Impact
Small Rx Buffers	512	1024	0.5% host mem increase
Rx Ring #1	1024	2048	Cluster stability improved

When encountering packet drops, check:

Get-Counter "\Network Interface(*)\Packets Received Discarded" -Continuous |
Where-Object {$_.CounterSamples.CookedValue -gt 0}

For ESXi host-level monitoring:

esxtop -b -n 1 -d 5 | grep "NET"