Udo, thank you for your reply. I will go RAID 1 for the Proxmox OS. The 72GB SAS are the only 'old' drives going in, and I have some spares, performance doesnt seem so bad. I guess ill try them out on a single node and get new drives for the others.
I am looking to setup a proxmox node with the following setup:
4x RAID 10 72gb SAS for proxmox installation on node (no VM's on this)
4x RAID 10 256GB SSD for VM's
8x 1TB SATA RAID 10 for backup
However I would like to place 6x RAID 10 SSD's, but I am wondering if a RAID 1 Mirror will suffice...