Load on promox installation drives

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 for the host OS. Is there little I/O on the Host's HDD array when a VM is on heavy load?