Windows 2012 Robocopy with Deduplication active

Solution 1:

Yes, you absolutely want to exclude "System Information Volume". Otherwise you risk wasting space on your source volume or corrupting already deduplicated files.

See https://support.microsoft.com/en-us/help/2834834/fsrm-and-data-deduplication-may-be-adversely-affected-when-you-use-rob

To complete your copy, you will probably have to set the dedup MinimumFileAgeDays setting to 0, and run robocopy more than once. When the copy fails due to lack of disk space, run dedup using the PowerShell command Start-DedupJob. Then run the copy again. You might have to repeat this process a couple of times until everything fits.