System and method for inquiry caching in a storage area network

A method for servicing inquiry commands, comprising:

• at a router connected to a plurality of sequential devices on a storage area network, receiving from a host device an inquiry command for inquiry data about a sequential device on the storage area network, wherein the sequential device is configured to sequentially process requests for data;
• determining whether or not the inquiry data is stored in a cache memory coupled to the router;
• if the inquiry data is stored in the cache memory, regardless of whether or not the sequential device is available, retrieving the inquiry data from the cache memory and returning the cached inquiry data to the host device in response to the inquiry command;
• if the inquiry data is not in the cache memory, determining whether or not the sequential device is available;
• if the sequential device is available, forwarding the inquiry command from the host device to the sequential device;
• and
• if the sequential device is not available, placing the inquiry command from the host device in a queue at the router, holding the inquiry command from the host device in the queue at the router until the sequential device becomes available, and forwarding the inquiry command from the host device to the sequential device for processing by the sequential device when the sequential device becomes available, thereby keeping the inquiry command from the host device from timing out.

A device for servicing inquiry commands, comprising:

• a cache memory for storing static or near-static data about sequential devices on a storage area network;
• a router coupled to the cache memory, wherein the router is configured to:
• receive from a host device an inquiry command for inquiry data about a sequential device on the storage area network, wherein the sequential device is configured to sequentially process requests for data;
• determine whether or not the inquiry data is stored in the cache memory;
• if the inquiry data is stored in the cache memory, regardless of whether or not the sequential device is available, retrieve the inquiry data from the cache memory and return the cached inquiry data to the host device in response to the inquiry command;
• if the inquiry data is not in the cache memory, determine whether or not the sequential device is available;
• if the sequential device is available, forward the inquiry command from the host device to the sequential device;
• and
• if the sequential device is not available, place the inquiry command from the host device in a queue, hold the inquiry command from the host device in the queue until the sequential device becomes available, and forward the inquiry command from the host device to the sequential device for processing by the sequential device when the sequential device becomes available, thereby keeping the inquiry command from the host device from timing out.