So, you have three disks - 1TB, 1TB, 2TB - in a RAID 0, and you are expecting to see 4TB of space?  If so, see my notes above.  Each Virtual Disk (RAID array) is presented to the OS as a separate "disk".  Windows cannot use a disk larger than 2TB unless it has been converted to GPT.  First, converting to GPT is data-destructive, so you would need to do a backup/restore.  Second, converting your boot "disk" to GPT will cause it not to boot on a 2950, because it doesn't support UEFI, which is required for booting to a GPT disk. Bottom line?  You need to rethink your configuration on this machine.  You could do two 1TB disks in a 1TB RAID 1 for the OS (being MBR and bootable on a 2950), and then you could add the 2TB disks in a RAID 1 for your data.  At 2TB, you would not need to convert to GPT, but if you added more than 2TB of space, you would then convert that to GPT and use as many TB for data as you can fit in the system. Also, you realize how dangerous running a RAID 0 is, right?
Good Day, I have an old PowerEdge II 2950 server (Specs: 2x3.0 Ghz Xeon, 24Mb Mem 1Tb SATA HDD,1Tb SATA HDD,2Tb SATA HDD - Server 2012 Datacenter). The issue that I am having is that I recently updated the OS from 2008 to 2012 DC, then installed an additional HDD (2TB).  I am running RAID 0, and the system is only showing a MAX avaliable HDD array space as 1.98 TB, with the remaining 0.02 Tb allocated for systems files.  The Perc 5i RAID controller has all three HDD's marked as online.  BUT I can not utilize the extra 2 TBs in the array.  I was going to purchase and install a 2nd 2TB SATA HDD and go to RAID 1; but, if I can't rectify this the un-represented storage space in the Storage Array I can not justify the purchase.  If any one can help I would be appreciative.
PowerEdge II 2950 not allowing HDD space to be accessed