Appeal 2006-2536
Application 10/611,127
an active-passive pair of storage controllers. Computers are known to
employ resource controllers. (Specification 1.) Most redundant arrays of
independent disk ("RAID") controllers, for example, operate in pairs, each
presenting an image of the same set of RAID arrays (or partitions of RAID
arrays) made out of storage shared by both RAID controllers. Active-
passive pairs of RAID controllers allow only one controller to access a
particular RAID array (or sometimes a partition of the RAID array) at a
time. (Id. 2.)
Allowing a single-requester system to access storage presented by an
active-passive pair of controllers is relatively straightforward. Various
software can detect the presence of an active and a passive controller, both
presenting the same storage, and can present them as a single storage device
or logical unit ("LUN") to the requester. (Id.)
In a multiple-requester system, however, "LUN thrashing" occurs
when different requesters attempt to make a different controller the active
controller of the pair. The result is that the role of active controller
repeatedly swaps. Because the time to swap the active controller is orders of
magnitude longer than the time to process an input/output ("I/O") request,
the result is a dramatic drop in the rate at which the controllers can process
I/O. (Id. 3.)
In response to detecting that each of two requesters has access to both
of an active-passive pair of controllers, the Appellants' invention designates
one of the controllers as an active controller. In response to detecting that
2
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 Next
Last modified: September 9, 2013