Infrastructure Architecture
On-premise and hybrid environments, datacentre platforms and roadmaps built for long-term operation.
Senior IT Systems Architect & Consultant
Infrastructure
for the real world.
I design, build and operate secure, stable and maintainable infrastructure — from architecture to production.
Independent consultant · Based in Czechia · Remote B2B collaboration
About
Reliable by design.
Practical by nature.
I’m Petr Kallen, an independent infrastructure architect and consultant. You work directly with me, from the first technical discussion through implementation and ongoing development.
I work across the full infrastructure lifecycle, from architecture, implementation and migration to recovery and long-term operations.
My focus spans on-premise and hybrid environments, virtualization, networks, security, monitoring and automation. I connect the individual parts into a coherent whole, with clear architecture and predictable behaviour.
Technology is not the goal. It is the tool for creating infrastructure that works.
Expertise
Systems thinking,
from rack to cloud.
Virtualization & Compute
Platform migrations, storage, clusters and resilient compute with recovery built into the design.
Systems and Platforms
Apple platforms alongside production Linux, Windows Server, identity and Microsoft 365.
Networking & Security
Network design, segmentation and secure access with FortiGate, MikroTik, OpenBSD and PacketFence. Routing, VPNs, Wi-Fi, RADIUS authentication and complex troubleshooting.
Automation & Development
Ansible, Bash, PowerShell and Python for practical automation, custom tools, repeatable deployments and dependable operations.
Monitoring & Resilience
Actionable monitoring, recovery-oriented backups, tested restores and realistic disaster recovery.
Collaboration
Expertise that fits
your team.
An experienced technical partner for IT service providers and in-house teams. Available for remote projects and ongoing collaboration across Europe.
Consulting & architecture
An independent review, a second perspective or a clear technical direction before a significant change.
Implementation & migration
Hands-on delivery from planning and preparation through implementation, verification and handover.
Long-term partnership
Continuity, knowledge of your environment and direct communication. Scope, availability and responsibilities agreed around your needs.
Technologies
Tools chosen
for the job.
The architecture leads. Technology supports it.
Virtualization
Hyper-V · KVM · Proxmox · VMware · XCP-ng
Containers
Docker · Kubernetes
Operating systems
Linux · macOS · OpenBSD · Windows Server
Identity & cloud services
Active Directory · Entra ID · Microsoft 365
Development & automation
Ansible · Bash · Git · PowerShell · Python
Apple app development
SpriteKit · Swift · SwiftUI · Xcode
Monitoring & backup
Nagios · Proxmox Backup Server · Veeam · Zabbix
Networks & security
FortiGate · MikroTik · PacketFence · RADIUS · TLS/PKI · VLAN · VPN · Wi-Fi
Selected Work
Complex environments.
Practical experience.
Virtualization platform migration
End-to-end transition of production workloads, storage, networking, backup and monitoring from VMware to Proxmox.
Hybrid Microsoft infrastructure
Integration of on-premise Active Directory with Microsoft 365 and Entra ID, including identity lifecycle and services.
Infrastructure recovery
Reconstruction of virtual infrastructure after storage or hardware failure, with backup consistency validation.
Monitoring architecture
Central observability for servers, networks and applications with useful alerting and integrations.
Custom software & automation
Custom tools, scripts and automated workflows connecting systems and simplifying repeatable operations.
Apps for iPhone & iPad
Native app and game development with Swift, SwiftUI and SpriteKit. Custom interfaces, engine integration and preparation for App Store submission.
Principles
How I approach
infrastructure.
Stability over novelty.
Newer is not automatically better.
Simple over complicated.
Every component should earn its place.
Security by design.
Security belongs in the architecture, not at the end.
Automation with purpose.
Automate repeatable work, not chaos.
Backup means restore.
Recovery is proven by testing it.
Beyond Infrastructure
Perspective comes
from stepping outside.
Away from infrastructure, you will most often find me in the mountains, on a mountain bike or behind a camera. Hiking, fitness, photography, aviation and drones share the same appeal: technology, movement and a little adventure.
Contact
Let’s build something
that keeps working.
Need an infrastructure consultation, an architecture review or an experienced partner for a complex project? Tell me about your environment, the challenge and what you want to achieve.
Emailpetr@kallen.czPhone+420 604 526 123Websitewww.kallen.czAddressPetr Kallennáměstí Odboje 300
544 01 Dvůr Králové nad Labem
Czech Republic
544 01 Dvůr Králové nad Labem
Czech Republic