Before continuing, you should have a RAID 5 array with a State: of Running. You can verify this using the Edit Components button that’s to the right of the State and see the health and status of each individual disk that currently makes up the RAID array. The State for the individual drives should be Fully Synchronized, this indicates that the drives all have current parity information for the other drives.
While you’re here, also note the Add Spare and Expand Array buttons. The Add Spare will not be addressed in this guide, but that function is there if you should ever want to research and use it.
The Expand Array button however, will be addressed below in the Configuration section of this guide.
Formatting the File System
Now, to finish the setup of this RAID array, select your RAID array, and find the Format Volume button. This will pop-up a small window with another drop down box. There are several options available here, however I strongly recommend using the default, EXT4.
Note: EXT4 is the default file system for Linux based operating systems (Ubuntu included). It is the direct successor of EXT3 (the previous default) and will eventually be superseded by BTRFS. It has been out for a few years now, the bugs seem to have been worked out, and it includes many nice features (such as checksumming) when compared to EXT3.
Type in the name for your volume, this can be the same as your RAID array’s name and, again, really doesn’t matter. Make sure Take ownership of filesystem is checked, and unless you know what you’re doing leave Encrypt underlying device unchecked.
When you’re happy, hit the Format button and the array will begin to format with the EXT4 file system (after a likely password prompt). This process will take some time, but should take considerably less time than the initial building of the array.