Method and Apparatus for Signalling Hot Failover in a Redundant I/O Subsystem
Original Publication Date: 2001-Jun-09
Included in the Prior Art Database: 2003-Jun-19
Disclosed is a mechanism for one adapter (dubbed the "Master") to disable a peer adapter (dubbed the "Slave"), and then restart the Slave adapter at a later time. The Slave adapter is held in stasis (i.e. the reset state) while the Master adapter performs any needed critical operations. The Master adapter is in complete control of the process and decides when the Slave adapter is to be disabled, how long to hold it in stasis, and when to restart it. When the Slave adapter is restarted it goes back through its initial bringup/boot phase again. The mechanism is accomplished with a direct connection between the adapters. No host operating system support is needed to support this function, resulting in a simpler implementation. The two adapters may even reside in separate enclosures, under different power domains, or even in separate systems. The adapter to be disabled is identified easily because it is implicit in how the system is cabled. This mechanism also is capable of meeting stringent time/performance constraints because the direct connection between adapters allows one adapter to be disabled immediately when required. An aggregation of the functional pieces described below forms a mechanism for controlling access to a shared resource by adapters. The mechanism provides the following functions for the peer adapters: The Master adapter can disable (aka "Fence") the Slave adapter.