Techniques are provided for processing an Input/Output (I/O) request. At least one data block is allocated for use in completing the I/O request. A current operations record is stored for the I/O request. It is determined whether the I/0 request has been completed within a specified period of time. In response to determining that the I/O request has not been completed within the specified period of time, the allocated at least one data block is fenced. Also provided are techniques for processing an Input/Output (I/O) request in which an identification message is received from a client computer. It is determined whether the client computer is a rogue client based on whether a current operations record exists for the client computer.