Space reporting in a storage system

An apparatus for space reporting in a storage system, the apparatus including a computer processor and a computer memory, the computer memory including computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

• determining, by a storage array controller, an amount of physical space and an amount of logical space consumed by each system-visible object referenced by a user-visible object;
• determining, in dependence upon the amount of physical space and the amount of logical space consumed by each system-visible object referenced by the user-visible object, by the storage array controller, an amount of physical space and an amount of logical space consumed by the user-visible object;
• determining whether the amount of physical space consumed by a particular system-visible object is less than a previously determined amount of physical space consumed by the particular system-visible object;
• and
• responsive to determining that the amount of physical space consumed by the particular system-visible object is less than the previously determined amount of physical space consumed by the particular system-visible object, reporting the particular system-visible object to a garbage collection process.