This issue occurs if the Cluster Shared Volume (CSV) volume is de-duplicated on a Windows RT 8.1, Windows 8.1, or Windows Server 2012 R2-based computer. In this situation, the defragmentation process runs at a speed less than one megabyte (MB) per second (1 MB/sec).
To resolve this issue, install update 2955164. For more information about how to obtain update 2955164, click the following article number to view the article in the Microsoft Knowledge Base:
2955164 Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 update rollup: May 2014
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates