We have a volume on a Server 2012 installation which is set up as a Fixed basic disk, with NTFS and with Deduplication enabled. Server Manager reckons it has made around a 34% saving through deduplication, equalling about 148GB.
If I go into the volume and select everything, and look at the properties, it shows the Size as 400GB, but the Size on Disk comes in at 3.89GB, which is obviously wrong.
If I go into a directory where I know a file is the only one of its kind (a compressed tar.gz file, which is a capture of a thin client image from Clonezilla), it says the file is 320MB but the size on disk is 4.0kb.
I can repeat this on nearly any file. Occasionally there is a file with 32Kb or so Size on Disk, but that's about it.
What's going on?