Intel ZT 4901 6.2.5.2 RhPrepareForSwitchover

High Availability Software for the Intel® NetStructureTM ZT 4901 Technical Product Specification 63

Redundant Host API

Hence, forced switchover is potentially destructive for the owning host and should be used with

care.

To perform forced switchover, it is sufficient to call the RhPerformSwitchover function. Forced

switchover can be initiated either by the owning host (in which case it voluntarily gives up control

of this domain), or by the new owner of the domain, or by some third-party host. In the last case, an

inter-host communication channel may be needed to request one of the immediately participating

hosts to perform the switchover.

After the switchover, software connection is automatically initiated for the relevant domains on the

receiving hosts.

Even in the case of a forced switchover request, there may be a possibility for the owning host to

intercept the hardware switchover request and prevent it via hostile actions with respect to the

destination host (for example, powering it off). An additional parameter (“Hostile”) to the

RhPerformSwitchover function can be used to perform unconditional (hostile) switchover without

any possibility for the owning host to prevent it.

After the switchover, software connection is automatically initiated for the relevant domains on the

receiving hosts.

This type of switchover is initiated by hardware in the case of a hardware-initiated alarm (for

example, a watchdog timer expiration) on the owning host. The new owning hosts for domains in

this case are specified in advance via RhSetHwDestinationHost function. The parameter Reset in

this function controls whether the PCI buses of the domain are reset after the switchover. If this

parameter is TRUE, the PCI buses of the domain are reset after the hardware-initiated switchove r,

which brings the devices into a known initial state on the new owning host.

The RhSetHwDestinationHost function can be called either on the owning host or on some third-

party host. In the last case, an inter-host communication channel may be needed to request the

owning host to register the destination host in hardware.

During hardware-initiated switchover, device operation is not quiesced and for the device drivers

and other software on the resigning host the PCI devices disappear, possibly in the middle of

transactions. However, this is not very important for this type of switchover, since the usual reason

for switchover in this case is a malfunction of the owning host that requires some corrective

actions, possibly including host reset.

After the switchover, software connection is automatically initiated for the relevant domains on the

receiving hosts.

6.2.5.2 RhPrepareForSwitchover

Prototype:

HSI_STATUS

RhPrepareForSwitchover(

IN RH_HANDLE Handle,

IN uint32 *pDomains,

IN uint32 DomainCount,