Hypervisor server Local storage Raid configuration

We have a couple of Dell PowerEdge R630 running Hyper-V and just bought new hard disks to fill all the empty slots. I was wοndering what kind of Raid configuration should we proceed.

Currently each server has 2x 300GB SAS on Raid 1 configuration where the OS and very few, critical, VMs live in a single volume/virtual disk. The rest of the VMs are stored in SAN iSCSI devices.

Now each server has in total 8x 300GB SAS drives and I think we have the following options:

1. Keep the Raid 1 Volume with the two drives for the OS and create a new Raid 6 Volume with the five drives for data. In this case i can keep one disk as a global hot spare (aka manual swapping in case of failure) for both raid volumes.


2. Combine all seven disks in a single Raid 6 Volume (one of the disks will be kept as a hot spare)
   
   
   
   
   
   • keeping the OS in a separe dell virtual disk and creating a new one for data.
   
   
   • expanding the current dell virtual disk to full size, ~1.4TB. I could then have two partitions or just have one huge partition.
   
   

I think in the past the norma would be closer to my first option, having the OS in Raid 1 and the data in Raid 5 volumes.

Since the hot spare drive is automatically swapping only when assigned on a Raid Volume, i would preffer to convert all drives in a single raid.

Considering the fact that we use SAS drives, should I be warried of any performance issues having both the OS and VMs on a single raid volume?

I would be glad to hear your opinions and expiriences.

Until now all of our servers would only have two disks in Raid 1 hosting the Virtualization OS (Hyper-v or vSphere), few VMs and the rest were offloaded to SAN/NAS iSCSI devices where we use Raid 5/6 depending the controller availability.
The plan is to keep using the SAN/NAS solutions in place but have the ability to store VMs locally too.