Fix for error 665: “The requested operation could not be completed due to a file system limitation”

How can this be? You may wonder, how come a 2TB file won’t copy into an drive with 2.8TB free. Instead of a nice copy progress, you get Windows error 665: “The requested operation could not be completed due to a file system limitation.”

What does this error mean and how do we resolve it?

A common issue here is that the OS limits the number of fragments a file may have. A quick look at defrag for the drive reveals:

Pre-Optimization Report:
        Volume Information:
                Volume size                 = 7.27 TB
                Free space                  = 2.83 TB
                Total fragmented space      = 65%
                Largest free space size     = 40.82 GB

So now we see the problem. Even though 2.83TB are free, the 2TB file can’t be copied into the space because the drive is heavily fragmented. Naturally it would have been great if the error message was a little more helpful. However, Microsoft wants to make sure IT people don’t run out of work, so it has these hidden “Easter eggs” to keep you occupied. As long as you get paid by the hour it’s good, right 😉

The fix?

Run defrag. Ideally run it twice. The second time with the /x option, to create as much free space in one area as possible. That way your new huge file will fit without fragments.