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After discovering PROXMOX for the first time, it evolved rather quickly. Quickly, most of the production machines around me were migrated. Without a support subscription, this software is free. PROXMOX is now in my case often the first choice when it comes to solving complex hosting problems.
PROXMOX supports KVM and containerization. With KVM, it can run virtually anything including Windows guests. Applications that can be containerized can be deployed in LXC containers, letting the guests use the full power of their hypervisor. This results in minimum ram usage and highest possible performance.
Integrated Ceph allows PROXMOX to be deployed as a hyperconverged infrastructure cluster. This makes the system capable of providing true high availability with built in fencing. Live migrations between physical nodes make maintenance and downtime planning easy.
PROXMOX also provides another, distinct software package called PROXMOX Backup Server, which seamlessly integrates into PROXMOX VE. It allows easy, fast, deduplicated and managed cluster wide backups. PROXMOX Backup Server is up until now by far the most reliable and easy to configure backup solution I have encountered.
Every guest on PROXMOX VE can be protected by a host based and web configurable firewall. This eliminates possible security risks and makes nodes capable of being hosted directly on the internet.