The images shown in this tutorial are based on CentOS 7. We will be using the GUI installer for configuring software RAID on setup. Setting up RAID after installation is a different process.

For this tutorial, I have setup a virtual machine with 4 HDDs.

1. When you start the CentOS GUI Installer, you will be presented with this screen.


Select "Installation Destination". It should show "No disks selected" as this is a new server.

2. Once on the "Installation Destination" screen, select all disks to be used in the RAID array. In this case, I have 4 disks that I will use. So I will select all 4 disks. 


A disk is selected when it has the black and white checkmark on it. We will be doing manual partitioning so make to tick the "I will configure partitioning" option under "Other Storage Options".


Click on "Full disk summary and boot loader" on the bottom left to configure boot options. By default it should be everything selected. Make sure to put the bootloader in a drive. In this case, I selected sda to install the bootloader on the first disk.


3. Now we'll create a /boot partition on the first disk. Make to specify the correct mount point and configure the desired capacity. In this case, I want the boot partition to be 1GB. Once done, click on "Add mount point".


Your new boot partition should be present in the partitioning screen now. On the right side, under Device(s), you should see that several disks are selected for the /boot partition. Click on "Modify".


Make to sure to select the first disk or whatever disk you installed the boot loader on. Click on "Select".


You should only see one device selected under Device(s) now.


Now add all the other partitions in your desired partition layout using the same process. But skip the selection under Device(s). In my case, I will only create a root partition.


4. Now we'll configure the software RAID. With the / (root) partition still selected on the left, click on "Modify" under Volume Group on the right. You should see the "Configure Volume Group" window pop up. By default it all disks are selected. In my case, I want it to stay that way since I will be using all 4 disks for my array.

The RAID level should display None at the moment. You can click on that and you can choose from the available RAID levels that you want to configure. For my case, I will configure RAID 0 and the size policy set to Automatic.


Once that's done it should bring you back to the partitioning screen. Click on "Modify" again to confirm that you have selected the correct RAID level that you want to configure. In this case, I can confirm I have selected RAID 0. Once done, Click on "Save" and then click "Done" on the partitioning screen.


You will be presented with a warning if you did not configure any swap partitions. In my case it is OK for tutorial purposes or if you have a server with high RAM. Just click on "Close" and click "Done" again to continue.


You will be presented with a summary of the changes to be made to disk. If this is acceptable to you, click on "Accept Changes" to begin writing the changes to disk.


Once that's done, the installation should continue on to the other steps.