HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 - (English) Advanc - Page 64

Primary and Alternate I/O Paths There are two I/O paths to each LUN on the disk array - one through controller A and one through controller B. Logical Volume Manager (LVM) is used to establish the primary path and the alternate path to a LUN. The primary path becomes the path for all host I/Os to that LUN. If a failure occurs in the primary path, LVM automatically switches to the alternate path to access the LUN. The first time an I/O is performed to the LUN using the alternate path, the disk array switches ownership of the LUN to the controller on the alternate path. Once the problem with the primary path is corrected, ownership of the LUN should be switched back to the original I/O path to maintain proper load balancing. The primary path established using LVM defines the owning controller for the LUN. This may override the controller ownership defined when the LUN was bound. For example, if controller A was identified as the owning controller when the LUN was bound, and LVM subsequently established the primary path to the LUN through controller B, controller B becomes the owning controller. 64 Disk Array High Availability Features