Enhanced network direct attached storage controller
An apparatus and method for providing a storage medium accessible across a network to a host. The storage medium's operation is generally controlled by a network disk controller. The network disk controller may receive a packet from a remote host, decapsulate the packet, and act on the packet to either transmit data from a storage medium or write data to a storage medium. Generally, the network disk controller does not execute any file system. Rather, the file system for communication between the host and controller is executed by the host. The performance of the network disk controller generally matches that of a local (i.e., non-network) disk controller in terms of data access and writing.
1. A method for accessing a storage medium across a network, the storage medium being operatively connected a network disk controller, comprising:
receiving a first packet from a first host at a first controller module of the network disk controller;
decapsulating the first packet into a header and a payload;
determining, from the header, a protocol associated with the payload;
determining whether the payload is associated with a non-network storage medium access command;
in the event the payload is associated with a non-network medium access command, executing the non-network storage medium access command;
assigning a communication link between an arbitrator and the storage medium to the first controller module;
receiving a second packet from a second host via a network at a second controller module of the network disk controller; and
controlling assignment of the communication link for one of the first packet and the second packet to reach the storage medium by the arbitrator;
wherein the executing the non-network storage medium access command comprises:
reading state information indicating whether the network disk controller is to operate in a command mode or a data mode, and
processing the payload based on the state information; and
wherein neither the network disk controller nor the storage medium executes a network file system.
2. The method of claim 1 , further comprising:
determining whether the communication link between the first controller module and the storage medium is assigned; and
in the event the communication link is assigned, preventing the second packet from reaching the storage medium.
3. The method of claim 2 , wherein the second packet is discarded in the event the communication link is assigned.
4. The method of claim 2 , wherein: the second packet is stored in a memory in the event the communication link is assigned; and
the second packet is passed to the storage medium when the communication link is no longer assigned.
5. The method of claim 1 , wherein controlling assignment of the communication link comprises:
determining whether the communication link between the first controller module and the storage medium is assigned by the arbitrator; and
in the event the communication link is assigned, preventing the second packet from reaching the storage medium by the arbitrator,
wherein the received second packet is handled as if the storage medium is directly connected to the second host.
6. The method of claim 5 , wherein the second packet is discarded in the event the communication link is assigned.
7. The method of claim 5 , wherein:
the second packet is stored in a memory in the event the communication link is assigned; and
the second packet is passed to the storage medium when the communication link is no longer assigned.