In some cases, you may need to add more disks to your existing guest machine on Virtualbox. Adding more disks to Virtualbox guest machine is very easy. After we add disks, we can then use the disk inside the guest machine for more storage space or we can use it to expand existing LVM disk.
To add new disks, follow these steps.
Open Virtualbox and click the guest machine we want to add disk. Next, click Settings.
The following animation should explain in better way. Click the image to see the animation