If you have 5x300GB disks in a RAID array, and the total size of the array is ~1.35TB, you can only have them in a RAID 0. Click on the RAID 0 to see the  member disks - you will probably see only one virtual disk, you will probably see all 5 disks as members of that VD, and you will probably see 0GB of available space on each. So, C: is 803GB ... what other partitions are there? In RAID 0, if a disk fails, EVERYTHING is gone. You are almost guaranteed to have some data loss already. I would recommend you get a backup, wipe out your RAID 0 and configure a larger RAID 5 (or 6 would be better).
Hi, I have installed Windorws 2012 R2 on my Poweredge R900 it has raid controller Perc 6/I with 5 SAS 300 GB HDD but i am not sure on what level of raid the OS installed. When I check the the disk manager C: drive shows 790 GB but as a Dell Virtual Disk shows 1.35 TB approx. Could any one please explain what level of raid the OS is on and how to check it.  Thanks
Installing windows 2012 R2 on Poweredge R900 with Raid