Veritas Storage Foundation 5.1 SP1 for Oracle RAC Administrator"s Guide (5900-1512, April 2011)

When the PreferredFencingPolicy attribute value is set as Group, VCS calculates
node weight based on the group-level attribute Priority for those service groups
that are active.
See the Veritas Cluster Server Administrator's Guide for more information on the
VCS attributes.
See “Enabling or disabling the preferred fencing policy” on page 131.
How disk-based I/O fencing works in different event scenarios
Table 1-2 describes how I/O fencing works to prevent data corruption in different
failure event scenarios. For each event, review the corrective operator actions.
Table 1-2
I/O fencing scenarios
Operator actionNode B: What
happens?
Node A: What
happens?
Event
When Node B is
ejected from cluster,
repair the private
networks before
attempting to bring
Node B back.
Node B races for
majority of
coordinator disks.
If Node B loses the
race for the
coordinator disks,
Node B panics and
removes itself from
the cluster.
Node A races for
majority of
coordinator disks.
If Node A wins race
for coordinator disks,
Node A ejects Node B
from the shared disks
and continues.
Both private
networks fail.
Restart Node B after
private networks are
restored.
Node B has crashed.
It cannot start the
database since it is
unable to write to the
data disks.
Node A continues to
work.
Both private
networks function
again after event
above.
Repair private
network. After
network is repaired,
both nodes
automatically use it.
Node B prints
message about an
IOFENCE on the
console but
continues.
Node A prints
message about an
IOFENCE on the
console but
continues.
One private network
fails.
49Overview of Veritas Storage Foundation for Oracle RAC
About preventing data corruption with I/O fencing