Why would you remove all the data? That doesn't sound like a good idea. Just upgrade the OS and then go through the normal upgrade flow of starting C* with the next version and upgrading sstables.
Also, *you will need to go from 2.0.14 -> 2.1.16 -> 2.2.8* and upgrade sstables at each stage of the upgrade. you cannot transition from 2.0.14 straight to 2.2.8.
