Add HDD to H730 mini(embedded)

We have a Dell R730 that is running ESX Host with below configuration
2-HDD Raid-1 for ISDM
4-HDD Raid-5 for Virtual Machines datastore
We want to add two more HDDs in the bays and configure those disks to Raid 1 virtual disk. Then I can move the OS to HDD from ISDM, which is not supported for ESXI7.
Can I create the virtual disk without losing the current configuration? If so, which option will take me to config F2 or Ctr+R?
I have upgraded the firmware and LCC to the latest. I will appreciate it if anyone walk me, though.