Asynchronous write errors

When an application program writes data to a file in an NFS-mounted file system, the write operation is scheduled for asynchronous processing by the biod daemon.

If an error occurs at the NFS server at the same time that the data is actually written to disk, the error is returned to the NFS client and the biod daemon saves the error internally in NFS data structures. The stored error is subsequently returned to the application program the next time it calls either the fsync or close functions. As a consequence of such errors, the application is not notified of the write error until the program closes the file. A typical example of this event is when a file system on the server is full, causing writes attempted by a client to fail.