I am hoping someone can help me. I just upgraded to the 2017 imac from a time machine backup. Before doing so I had around 200 GB's of free space but now my new system is completely maxed @ 1 TB! The system storage shows 289 GB's being used and I do not know what for. I can identify all my other large files but I cannot drill into what is using this space. I have used OmniDisk Sweeper as well as Disk Inventory X. They only give me feedback on my normal files that I am already aware of. This system allocation is driving me crazy as I have no local disk space now! I have tried everything I can think of -save purging the actual files I want to keep. I am not finding duplicates or any rogue file creating caches or logs. I simply do not know where this came from - what its for or how to access it and delete it. As you can see from my screenshots Disk X is showing max usage @ nearly 1 TB, but when you expand it to see details the 289 GB is unaccounted for on the HD volume.