VM Limitations & Pitfalls

VM Limitations & Pitfalls#

The Cost of Ultimate Isolation While hardware virtualization provides comprehensive isolation, it introduces structural and operational burdens that must be managed to maintain reproducibility and cluster efficiency.

Operational Pitfalls#

❄️ Configuration Drift

The “Snowflake” Server Manual SSH modifications create undocumented, fragile environments that cannot be replicated.

Mitigation: Treat VMs as Immutable Infrastructure. Automate all configurations via Ansible, Puppet, or cloud-init.

🛡️ Maintenance Burden

Independent Entities Unlike containers, VM owners assume full responsibility for:

  • Guest OS security patches.

  • Firewall configurations (ufw, iptables).

  • Routine updates (apt-get upgrade).

Hardware Limitations#

🛑 Resource Inflexibility

  • Hard Reservations: CPU and RAM are fully locked by the hypervisor.

  • Resources cannot burst or share idle cycles seamlessly across the host.

  • Results in lower overall utilization density on compute clusters.

🔌 Pass-through Complexity

  • Direct access to GPUs/InfiniBand requires PCIe Passthrough or SR-IOV.

  • The hypervisor detaches the device from the host and maps it to the VM memory space.

  • Trade-off: Breaks advanced features like live-migration, limiting high-availability.

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