which Acronis backup product are you using? True Image 20xx or Acronis Backup?
What type of Backup were you trying to do? a System Backup of your C:\ Drive or a Files & Folder backup of your C:\Drive?
I do know with True Image you can select what you want to backup but in a System Backup you just pick the C:\ Drive you want backed up.
I would contact Acronis Support and find out if Acronis is able to do a System Backup with RAID or STOREMI type configuration on a computer.