DFS Similarity Table

I have a server running Windows Storage Server 2003 R2 w/SP2 which is a member of a DFS replication group. Every so often backups fail due to issues with the DFSwriter being used by Backup Exec. It seems to occur when the OS wants access to the writer so BE obliges and it fails the job. While investigating this I found that the DFS folder was talking up a large amount of space (about 9GB). All of the data is being taken up by the SimilarityTable_1 file located in C:\System Volume Information\DFSR.

So my question is, why is the SimilarityTable file taking up so much space? Is there anything that can be done to reclaim the space?
dfs.jpg