Combining multiple physical servers to function as a single logical unit is achieved through server clustering technologies. This approach aggregates compute resources (CPU, RAM, storage) to create a unified pool that can host multiple virtual machines with better performance and fault tolerance than individual servers.

Several mature solutions exist for creating such cluster environments:

• VMware vSphere with vMotion and DRS: Allows live migration of VMs across physical hosts
• Microsoft Failover Clustering: Provides high availability for Windows Server environments
• Proxmox VE: Open-source solution with built-in clustering capabilities
• Red Hat Cluster Suite: Enterprise-grade Linux clustering

Here's how to set up a basic 3-node Proxmox cluster:

# On first node (master):
pvecm create mycluster

# On subsequent nodes:
pvecm add IP_OF_MASTER

# Verify cluster status:
pvecm status

Once nodes are clustered, you can create shared storage pools and allocate resources:

# Create a shared ZFS storage pool
zpool create clusterpool mirror /dev/sdb /dev/sdc

# Configure in Proxmox GUI:
Datacenter -> Storage -> Add -> ZFS

When launching new VMs, the cluster automatically handles resource distribution:

qm create 100 --name vm1 --memory 4096 --cores 2 \
--net0 virtio,bridge=vmbr0 --scsihw virtio-scsi-pci \
--scsi0 local-zfs:8,format=qcow2

Key factors affecting clustered VM performance:

• Network latency between nodes (10Gbps+ recommended)
• Storage synchronization overhead
• CPU architecture compatibility
• Memory ballooning configuration

Example of manual VM migration between nodes:

qm migrate 100 node2 --online --with-local-disks

What we're essentially discussing here is creating a unified computing resource pool from multiple physical servers. This concept goes by several technical terms in the infrastructure world:

• Server clustering
• High-availability virtualization hosts
• Distributed resource scheduling
• Compute fabric

Several mature solutions exist for creating such clustered environments:

# Example of using Pacemaker for cluster management
pcs cluster setup --name MY_CLUSTER node1 node2 node3
pcs cluster start --all
pcs property set stonith-enabled=false
pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.1.100 cidr_netmask=24 op monitor interval=30s

For VMware environments, vSphere's High Availability (HA) and Distributed Resource Scheduler (DRS) provide this functionality:

# Sample PowerCLI commands to configure HA
Connect-VIServer -Server vcenter.example.com
Get-Cluster "Production" | Set-Cluster -HAEnabled $true -HAAdmissionControlEnabled $true
Set-Cluster -Cluster "Production" -DRSEnabled $true -DRSAutomationLevel FullyAutomated

The Proxmox VE solution offers similar capabilities:

# Creating a Proxmox cluster
pvecm create CLUSTER_NAME
pvecm add IP_OF_FIRST_NODE

For modern deployments, consider solutions like:

• Nutanix AHV
• Microsoft Storage Spaces Direct
• VMware vSAN
• Ceph with KVM