System and method for multipath I/O support for fibre channel devices
A system and method enables a file server, to support multi path input/output operations for Fibre Channel devices. Upon each Fibre Channel Arbitrated Loop initialization event generated, the system and method updates a path and device instance to track multiple paths to a given device. While the file server is attempting input/output operations, the failure of a given path can be corrected by the use of another path associated with a given device. The data structures generated by the low levels of the storage operating system are exposed for use by upper level services for routing a storage device identification purposes.
1. A method for maintaining a set of data paths accessible by a set of upper level services of a storage operating system of a computer, the method comprising the steps of:
creating a device instance associated with a storage device;
creating a first path instance distinct from the device instance, where the first path instance is associated with a first path to the storage device;
creating, in response to events identifying an addition of a path, an additional path instance associated with an additional path to the storage device, where the additional path is distinct from the device instance; and
deleting, in response to events identifying a removal of a path, a path instance associated with the removed path.
2. The method of claim 1 wherein the step of creating a device instance occurs in response to receipt of an event identifying an addition of a storage device.
3. The method of claim 1 wherein the events identifying an addition of a path is a Fibre Channel loop initialization event.
4. The method of claim 1 wherein the events identifying removal of a path is a Fibre Channel loop initialization event.
5. The method of claim 1 wherein the step of creating an additional path instance further comprises the step of linking the additional path instance to a linked list of path instances associated with the storage device.
6. The method of claim 1 wherein the device instance and path instances are accessible via an application program interface.
7. The method of claim 1 wherein the set of upper level services further comprises a redundant array of inexpensive disks layer of the storage operating system.
8. The method of claim 1 further comprising:
dynamically generating the set of data paths in response to a storage device event.
9. The method of claim 1 further comprising:
selecting, as the first data path, a last used data path associated with the storage device.
10. The method of claim 1 further comprising:
performing the input/output operation to a disk drive as the storage device.
11. The method of claim 10 further comprising:
interconnecting the computer with the disk drive by a Fibre Channel Loop.
12. The method of claim 1 further comprising:
performing the input/output operation from a file server as the computer.
13. A computer-readable medium, including program instructions executing on a computer, for maintaining a set of data paths accessible by a set of upper level services of a storage operating system, the program instructions including steps for:
creating a device instance associated with a storage device;
creating a first path instance distinct from the device instance, where the first path instance is associated with a first path to the storage device;
creating, in response to events identifying an addition of a path, an additional path instance associated with an additional path to the storage device, where the additional path is distinct from the device instance; and
deleting, in response to events identifying a removal of a path, a path instance associated with the removed path.
14. An apparatus for maintaining a set of data paths accessible by a set of upper level services of a storage operating system of a computer, comprising:
means for creating a device instance associated with a storage device;
means for creating a first path instance distinct from the device instance, where the first path instance is associated with a first path to the storage device;
means for creating, in response to events identifying an addition of a path, an additional path instance associated with an additional path to the storage device, where the additional path is distinct from the device instance; and
means for deleting, in response to events identifying a removal of a path, a path instance associated with the removed path.