I have found the solution, the problem was that hard disk Master Boot Record was not present. I run an Ubuntu Live CD and setup it. The hard disk is already detected and the installation was successful. Thanks a lot!
Hello everyone! Its the first time Installing Ubuntu Server on a Power Edge 2950 to me and  The issue is when it comes to partitioning disks, it said it has detected active SATA drives there - "One or more drives containing Serial ATA RAID configurations have been found. Do you wish to activate these RAID devices? Activate Serial ATA RAID devices. I was given two options "yes" or "no". I clicked "Yes" because I thought this would enable ubuntu server to set up RAID1 during the installation. However, I was brought to the Partition disks that says "This is an overview of your currently configured partitions and mount points. Select a partition to modify its settings...., then there are three options to choose namely: Configure iSCSI volumes Undo changes to partitions Finish partitioning and write changes to disk  So I am not sure if I am doing the write thing here. When I chose "Configure iSCSI volumes", I was prompted to choose either Log into iSCSI targets or Finish. I do not know what to do from here.   Any help would be greatly appreciated.  Thank you
Configure iSCSI Volumes