Currently, when FTDC file writer fails to open a file, it returns a FileNotOpen status but with very little context on why it failed. This Status is then uassert-ed in the main FTDC loop, throwing an unhandled exception that shuts down the server. Often, the main cause is either the host machine has no space left on the device, or the number of open file descriptors have reached the system/process limit. It would be nice if the root cause is immediately obvious from the log line emitted by the fatal assertion.