Part of the benefit of the alternate installer is that it allows us to install Ubuntu in ways that aren’t normally available with the live installer. One of the additional features is to be able to install Ubuntu on software RAID, which is what we will do in this section. Here, the steps that we’ll go through actually continue on from step 14 in the previous section. Follow these steps to set up an installation with software RAID, specifically with RAID1 between two disks in this case.

1. In the previous section, we chose  Guided – use entire disk at the screen shown in the following screenshot. To set up RAID, we’ll select  Manual on this screen instead:

2. Next, we’ll select the first disk and press  Enter:

3. Next, you’ll be asked whether you will want to create a new partition table on this disk, which will wipe all data on it. Choose  Yes and press  Enter:

4. On the next screen, select the second disk (the one we haven’t initialized yet) and press Enter:

5. You’ll again be asked whether you wish to create a new partition table. Select  Yes and press  Enter:

6. On the next screen, we’ll choose the  Configure software RAID option:

7. Before we can continue, the installer must finalize the changes we’ve made so far (which at this point has only been to initialize the disks). Select  Yes and press  Enter:

8. Next, choose  Create MD device and press  Enter:

9. Next, we’ll select the type of RAID we wish to work with. Select  RAID1 and press  Enter to continue:

10. Next, choose the number of disks we will add to RAID1. RAID1 requires exactly two disks. Enter 2 here and press  Enter:

11. If we have additional drives beyond two, we can add one or more hot spares here. These will be used in the event of a failure with one of the RAID disks. If you have an extra disk, feel free to use it and enter the appropriate number here. Either way, select  Continue and press  Enter:

12. Next, we will choose which disks to include with our RAID1 configuration. We should have exactly two listed. Use the  arrow keys to move between them, and press  Space to select a disk. We need to select both disks, which means we will be marking both with an asterisk ( *). Once you’ve selected both disks, select  Continue and press  Enter:

13. Next, we’ll finalize our selections so far. Select  Yes and press  Enter:

14. Select  Finish to continue on:

15. Now, we have successfully set up RAID. However, that alone isn’t enough; we need to also format it and give it a mount point. Use the arrow keys to select the RAID device we just set up and press  Enter:

16. Using the following screenshot as a guide, make sure you set  Use as to  EXT4 journaling file system (you can choose another filesystem type if you wish to experiment). In addition, set the  Mount point to  / and then select  Done setting up the partition:

17. To finalize our selection, choose  Finish partitioning and write changes to disk:

18. Next, we’ll see one last confirmation before our new partition will be created. Select  Yes and press  Enter:

That pretty much covers the process of setting up RAID. From here, you can return to the previous section and continue on with the installation process with step 16. Once you finish the entire installation process, it will be useful to know how to check the health of the RAID. Once you log in to your new installation, execute the following command:

cat /proc/mdstat

In the previous screenshot, you can see that we’re using RAID1 (look for the section of the output that reads active raid1). We an also see whether each disk in the RAID array is online, looking for the appropriate number of Us. It’s this line:  20953088 blocks super 1.2 [2/2] [UU]

If the output included U_ or _U instead of UU, we would have cause for alarm, because that would mean one of the disks encountered an issue or is offline. Basically, each U represents a disk, and each underscore represents where a disk should be. If one is missing and changed to an underscore, we have a problem with our RAID array.