Learn how to expand your ZFS zpool on a VPS by expanding the raw disk, and then expanding the ZFS filesystem to make use of that expanded disk.
Learn how to add a disk in Linux. Create a partition table, before adding a partition and adding a filesystem to it. Then set it up to automatically mount on boot.
Learn how to run the secure erase procedure on your hard drive in order to truly delete all the data on there. This will also improve an SSDs performance for when you next use it.