I need to build two Proxmox Backup Servers (on site and off site) for a project (formerly a home project, now a work project) and for space constraints at one of the offices I need the backup server to be smaller than your averrrage 1U server. I'm planning to put pretty basic hardware into them. I think Proxmox Backup Server will run fine on a Xeon-D board orchestrating 4x 16TB disks as a backup target. I prefer having both of the enclosures be identical. I also prefer not paying the extra premium for a QNAP or Synology. I know this isn't strictly a n r/homelab question, but it makes more sense here than anywhere else.

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So I'm looking for:

- Bare minimum ITX (or similar) recommendations for running Proxmox Backup Server, maybe with an M.2 for the OS.

- A small 1U case that can take 4x 3.5" drives