Failover (Network cards)
Failover is an MDI feature
that allows networking traffic to be shifted
to a different configured network adapter card
when hardware failures are detected on the original card.
Three types of failover support are available
for SVR5 MDI devices:
PCI hotplug failover
Requires hardware that implement PCI hotplug failover
(for example, Compaq Proliant 6500, Proliant 7000, and IBM)
and a DDI 8 MDI driver that implements
the CFG_SUSPEND and CFG_RESUME subfunctions
entry point routine.
This allows the system administrator
to suspend the driver, power down the slot,
hot-swap or hot-replace the network adapter card,
power up the slot, and resume the driver,
all without bringing the machine down.
Your driver does not need to send up
For MDI versions 2 and 2.1,
this works only with DDI 8 and later drivers
for PCI adapters.
Reliant non-stop clustering
Requires that your driver be able to program
MAC addresses and its own address with the
This works with any
DDI 7 or DDI 8 MDI driver
on any bus type.
The DLPI subsystem listens for
messages and initiates a failover
if the failover criteria are met.
The system administrator has the ability to set failover criteria:
for some sites, a single MAC_HWFAIL_IND message
may be an indication to move all traffic
to another failover network adapter card.
Note that all the network adapter cards
must already be present in the machine
and that failover is an automatic process
after it is initially configured;
no user intervention is required to switch to a new card.
The Network Configuration Manager
is used to configure a failover adapter.
It also provides the ability to force a failover
and to failback to the original adapter
after the problem is resolved.
This is useful for testing as well as administration.
With appropriate hardware,
you can combine the hot-swap and general failover features.
This enables the user to hot-swap the primary network adapter card
after a failover,
then failback to the replaced card.
General failover works with
any MDI versions 2 or 2.1 driver
on any bus type.
All MDI drivers should be written
to support failover from the card.
Driver must send up a
message to indicate that it has problems.
The driver for any device that can detect a fatal error
should send up this message,
whether or not it claims to support failover.
This is not required for PCI hotplug devices.
Driver must fully re-initialize the adapter
followed by a subsequent open of the device.
Remember that an MDI driver's
routine must disable interrupts on the card
and the driver's
routine must fully initialize the card.
If the card cannot be reset, the
routine should fail.
For MDI drivers, the /dev/mdi device
is exclusive open.
Criteria for failover to your card:
You can use the Network Configuration Manager
to configure a failover device for your adapter
and test failover as follows:
Generate traffic to another machine with
the ping -s <remote> command.
Run nd failover net<X>,
where net<X> is the net[0-9] device
configured over your driver.
all configured net<X> devices
associated with MDI drivers.
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005