Methods of providing access to I/O devices

1. A method of providing one or more computing devices with access to a plurality of resources, the plurality of resources being provided by at least one physical device, the method comprising:

receiving data by a first control element from a second control element, said data indicating a plurality of first logical identifiers each being used by the second control element to identify a respective resource of the plurality of resources;

storing data at the first control element defining relationships between said plurality of first logical identifiers and a plurality of second logical identifiers associated with at least one of said one or more computing devices;

receiving a first request from one of said one or more computing devices, the request including one of the second logical identifiers;

using said one of the second logical identifiers to obtain one of the first logical identifiers based on the stored data; and

transmitting a second request including said one of the first logical identifiers to the second control element, the second control element being arranged to identify a physical device to provide the respective resource of the plurality of resources associated with said one of the first logical identifiers;

wherein each of the plurality of second logical identifiers is used by at least one of the one or more computing devices to identify one of the plurality of resources.

2. The method of claim 1 , wherein said data indicating the plurality of first logical identifiers is received in response to a request from said first control element to said second control element.

3. The method of claim 1 , further comprising blocking access by said one or more computing devices to the at least one physical device before receiving data by the first control element from the second control element.

4. The method of claim 1 , further comprising receiving data indicating relationships between said plurality of first logical identifiers and the plurality of second logical identifiers associated with at least one of said one or more computing devices.

5. The method of claim 4 , wherein said data indicating relationships between said second logical identifiers and said first logical identifiers is based upon user input.

6. The method of claim 1 , further comprising:

storing data defining a plurality of relationships between at least one second logical identifier and the plurality of first logical identifiers, wherein each of said plurality of relationships is associated with a respective computing device.

7. The method of claim 1 , further comprising identifying ones of the first logical identifiers in response to receiving indications of second logical identifiers from the one or more computing devices and providing indications of the first logical identifiers to the second control element.

8. The method of claim 1 , wherein storing data at the first control element defining relationships comprises storing data indicating which of the one or more computing devices is validly associated with each of the second logical identifiers.

9. The method of claim 1 , further comprising:

validating said one of the second logical identifiers with reference to the computing device that issued the request; and

obtaining said one of the first logical identifiers only if said second logical identifier is valid.

10. The method of claim 1 , wherein said plurality of resources comprise a plurality of logical storage units.

11. The method of claim 10 , wherein each of the plurality of logical storage units comprises storage provided by one or more non-volatile storage devices.

12. The method of claim 1 , wherein said plurality of resources comprise a plurality of Fibre Channel virtual ports.

13. An apparatus for providing one or more computing devices with access to a plurality of resources, the plurality of resources being provided by at least one physical device, the apparatus comprising:

a first control element which includes:

a first interface arranged to receive data from a second control element, said data indicating a plurality of first logical identifiers each being used by the second control element to identify a respective resource of the plurality of resources;

a memory for storing data defining relationships between said plurality of first logical identifiers and a plurality of second logical identifiers associated with at least one of said one or more computing devices wherein each of the plurality of second logical identifiers is used by at least one of the one or more computing devices to identify one of the plurality of resources; and

a processor arranged to use the stored data to obtain one of the first logical identifiers in response to receiving one of the second logical identifiers from one of the one or more computing devices; and

a switching device in communication with the first control element and arranged to forward data packets received from the one or more computing devices to the first control element if it is determined that the data packets satisfy a predetermined criterion.

14. The apparatus of claim 13 , further comprising a second interface arranged to transmit the obtained one of the first logical identifiers to the second control element.

15. The apparatus of claim 13 , wherein the switching device is further arranged to forward data packets received from the one or more computing devices to the at least one physical device if it is determined that said data packets do not satisfy the predetermined criterion.

16. The apparatus of claim 13 , wherein said plurality of resources comprise a plurality of logical storage units.

17. The apparatus of claim 16 , wherein each of the plurality of logical storage units comprises storage provided by one or more non-volatile storage devices.

18. The apparatus of claim 13 , wherein said plurality of resources comprise a plurality of Fibre Channel virtual ports.