Why is my actual storage half that of Plan?

This can happen if you have resized your Linode to a larger plan without having resized your Linode's disk. Resizing to a larger plan does immediately grant you a larger disk allocation but does not automatically resize your disk partition without your approval.

Prior to resizing, you can have your disk automatically increase by selecting the "Auto Resize Disk" option. However, if you have already completed your plan resize, you will be able to resize your disk by following the guide linked below:

• How to Manage Disks and Storage on a Compute Instance | Linode Docs

Otherwise, if you have created more than one disk partition (sdc, sdd, etc) and do not have those disks currently mounted to your Linode, that could be why your system does not report the full allocation amount. For more information about mounting disk partitions to your Linode or any Linux system, be sure to read the following Docs page:

• Linux Mount Command: Mounting File Systems & Disks | Linode Docs