RESCALE
Do you need more performance? Just scale up to a more powerful plan.
You have the option to rescale your CPU and RAM only and leave your server's disk untouched or expand the disk as well. A downgrade is only possible if you leave the disk as is. You are not able to downgrade to a plan with a smaller disk.
Your server needs to be powered off, in order to be rescaled. The process will usually take just a few minutes.