The idea of splitting your Ubuntu installation between two hard drives is a concept that isn’t new. The idea often comes up from those that are looking to spread out one Linux installation onto different hard drives, for many reasons. One of the main reasons users split Ubuntu is to compensate for the small sizes of solid state drives, For example: when you have an SSD and a large 1TB 7200 RPM drive. You want to benefit from the break-neck speeds of an SSD, but you realize it’s small. That’s when you realize that you’ve also got a large second hard drive. With this method, it’s possible to split half of the Linux installation onto the SSD, and the other onto the RPM one.
In this tutorial, we’ll focus on Ubuntu, as the installation tool is the most straight forward, and easiest to understand when it comes to splitting up an installation. That said, the basic concept is easily repeatable on many types of Linux distributions (both complex and beginner ones).
Hard Drives & Solid State Drives
Understand that this method doesn’t require an SSD. It just so happens that SSDs are usually expensive the larger they get. As a result, many Linux users find ways to “expand storage” on their machines. “Splitting up” an installation is the preferred method. Any two hard drives will work with this process, as will a hard drive and a solid state drive.
Note: as SSDs are faster, we’ll use this as /dev/sda. The RPM hard drive should be /dev/sdb.
Before installing Ubuntu, get your drives ready for the installation process. Be sure that all of the data on these two hard drives is backed up, as everything on them will have to be deleted. The Ubuntu custom installation tool will format them to create a new file system.
Note: it is possible to mount an existing, in use file system as a second drive, but it’s recommended that you instead start fresh with a new file system for drive health reasons.
With the drives prepared, download Ubuntu. Any Ubuntu version, or flavor will do as the installation tool is what matters here. Once downloaded, go to the Etcher website, and make a live disk. Then, use your PC’s BIOS to load from it.
As you load up the Ubuntu live disk, a greeting screen appears with two options. Select the option to “Install Ubuntu”. Clicking this option will kick off the pre-setup process. This process involves selecting several options for your new installation. Go through, read, and check the boxes for everything you want in your new installation.
When done, make your way to the “Installation Type” window. In this section, the only option that matters is “Something else”. Select this option, and the “continue” button to be taken to the custom install section.
What follows is the Ubuntu Ubiquity partition tool. In this window, you’ll need to manually assign mount-points for your new installation.
Note: Start off by selecting /dev/sda in the partition layout tool. If there isn’t a file system on it, click “New Partition Table” to create a new one. Do the same with the second drive (/dev/sdb)
The BIOS/MBR partition layout is very simple, as there is no need for a special boot partition. The first step is to create the “root” drive. Select the free space under /dev/sda, and click + to create a new partition. Multiply 1024 times however many to convert MB to GB.
For example: the entire /dev/sda hard drive is 14 GB. I’d like to make a root partition of 12 GB, so I’d do: 1024 x 12 and get 12288 MB.
Enter your own conversion into the “Size:” area, click “mount point” and set it to /. Click OK to accept the changes.
Next, create a SWAP partition. Select “free space”, click +, look for “use as” and choose “swap area”.
Note: If you use an SSD, strongly consider skipping the swap partition/file as it contributes to excessive writes.
Lastly, click on the “free space” section under the /dev/sdb drive, select the + sign and create a new partition. Don’t worry about conversion, as this partition should fill the entire hard drive. Find “mount point”, and select /home.
After all three partitions are set up, click the install button to finish the rest of the Ubuntu installation process.
The instructions for UEFI Computers is identical to the MBR/BIOS mode with one difference: the boot partition. Before doing anything, select “free space” on /dev/sda and click + to create a new partition. Under size for this partition, enter 512 MB. Then, select find “use as” and select the option “Use as EFI system partition”.
Note: the installer will round 512 MB down to 510 MB. Do not worry! Everything is fine. A lot of times, the Ubuntu installer doesn’t reflect the exact numbers users input.
When the EFI system partition set up in the installer, the hard part is done. From here, go to the instructions above, and follow them.
Lost? Take a look at the picture below. Your EFI partition layout for Ubuntu will be similar.