New Mac Mini Lion Server Extensive Lag times

I have recently installed a MacMini at a clients of mine, running a Pegasus R4 Thunderbolt RAID. My client is noting extensive lag times when copying to the server. He notes that the progress bar completes and then it hangs there for a min or two, then releases. The same is happening when they attempt to delete, it lags for some time. I would love some assitance if anyone can help. Thanks.