I'm trying to copy several terabytes from one server's 4TB Storage Space to another server's 4TB Storage Space, but the copy is failing due to the Storage Space on the second server running out of room with over 600GB of additional invisible phantom data.
Server 1 (Source): Windows Server 2012 Essentials, 4TB (3.63 TB formatted) mirrored ReFS Storage Space, file integrity streams enabled. Storage Space contains 3.01TB worth of files, with 554GB free space.
Server 2 (Destination): Windows Server 2012 Essentials, 4TB (3.63 TB formatted) mirrored ReFS Storage Space, file integrity streams enabled.
File copying is done over the network from Server 1 using FastCopy with Verify enabled.
The file copy fails at about 3TB worth of files, with Windows Explorer on Server 2 reporting the destination 3.63TB Storage Space volume as being completely filled. Windows Explorer reported the folder with the transferred files as being just about 3TB. This leaves 652GB worth of something filling the volume completely unaccounted for.
There are no other files or folders on the volume containing this 652GB. The transferred data is the only folder in the root of the volume, apart from the Recycle Bin and (possibly the first time) System Volume Information (the only other obvious places to look for the phantom data).
There are no shadow copies on this volume according to
vssadmin list shadows, and
vssadmin list shadowstorage does not show any shadow storage on the volume.
I have tried running several disk usage utilities - WinDirStat, TreeSize, and SpaceSniffer - and only TreeSize could even see there is something else filling the volume besides the 3TB of transferred data. However, TreeSize reported this 652GB of something as "Unknown".
I even tried running several of these utilities under the Local System account, including Sysinternals' Du (disk usage), and it didn't change anything. The utilities still couldn't see there was something filling up the extra space (aside from the aforementioned TreeSize), let alone any details on what the phantom data might be.
I deleted the volume, the Storage Space and the Storage Pool on the destination server and then rebuilt them from scratch and started the file copy again. Halfway through the file copy process I checked, and there was already nearly 300GB worth of unaccounted for data on the destination server's Storage Pool volume.
Near the end, at the nearly 3TB mark, the file copy failed again, just like the first time, with the hundreds of gigabytes of something filling up the rest of the volume. Again.
Anybody have any idea what is going on here?