VM local storage requirement of the VM machines for running a testnet

We have been running a COSMOS testnet in our own cloud VPC; With that being said, we have kept 2 full nodes, 3 validators and other seed/sentry nodes as well, there is problem for us, the limited persistent volume may put a constraint upon the increasing amount of storage, the storage files are piling up (I have to adjust the storage capacity from time to time). half a year ago it was 150GB, now it becomes 240GB for each node.

I am not a very experienced blockchain user, and I have done my best researching on the subject; Could someone here offer any recommendations; is there any approach to reduce the storage footprint without starting a new testnet (We have already got some cosmos smart contract running in it); or at least keeping the storage need under control.