By default, installing Proxmox with ZFS during the installation process will force you to use the entire disk for the root zpool. For most installs this is good enough. However, I like to do things differently sometimes.
I have a pair of Samsung 840 Pro 256GB SSDs that I wanted to use for my new homelab that I am currently building (moving from vmware to proxmox). You may be wondering why I want to install the operating system on a partition instead of an entire disk. Several reasons: