When comparing Proxmox vs TrueNAS (formerly FreeNAS), the Slant community recommends TrueNAS (formerly FreeNAS) for most people. In the question“What are the best operating systems for a NAS/File server?” TrueNAS (formerly FreeNAS) is ranked 2nd while Proxmox is ranked 6th. The most important reason people chose TrueNAS (formerly FreeNAS) is:
It has full support for the Solaris ZFS filesystem.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free
Free with no restrictions like missing backup facilities.
Pro Native ZFS support
It has full support for the Solaris ZFS filesystem.
Pro Traditional Init-system
It uses a traditional UNIX init system.
Pro No systemd
So if some errors appear on boot the system will still boot and you can repair it via ssh.
Pro Solid BSD core
It runs on the stable FreeBSD kernel.
Pro Can use plugins
It's able to use Plugins.
Pro Many Plugins
There are many plugins available.
Pro VSS (Volume Shadow Copy) supported natively in SMB (Samba)
Cons
Con No Windows installer
Proxmox is Debian based, and although it can be installed in an existing Debian system it is easier to install from the .iso image.
Con Permissions and sharing is not user friendly
For example, WebDAV access is limited to the single "webdav" user. Also, no other folks can log in to the main NAS UI besides the admin.
Con Only AMD64 (x86-64)
It does not have support for other CPU architectures.
Con Limited hardware support
BSD has less support for newer hardware compared to Windows or Linux.