Prioritizing virtual volumes to take offline in a thin provisioning system with garbage collection. The method categorizes virtual volumes based on garbage collection properties of their write behavior and adds metadata indicating a category of a virtual volume. The method schedules virtual volumes to be taken offline by predicting virtual volume space utilization of active virtual volumes for a defined time period in combination with estimated garbage collection in that period to determine a need to take virtual volumes offline. The method selects virtual volumes to take offline by their category to ensure that the virtual volumes producing the most garbage collection unfriendly workloads are taken offline first.