Thin Provisioning
Allocating storage on demand, so volumes can be defined larger than the physical space currently used.
Thin provisioning is common with LVM-thin and ZFS zvols in Proxmox. It saves space and enables fast snapshots, but you must monitor real usage — overcommitting and then filling the pool can take everything offline.
Related articles
ZFS
An advanced filesystem and volume manager offering data integrity, snapshots, compression and software RAID.
Snapshot
A point-in-time, read-only copy of a filesystem or volume that lets you roll back changes instantly.
Hypervisor
Software that creates and manages virtual machines by allocating physical resources between them.