How I/O Fencing Works In Different Situations - Symantec XGS-4728F Installation Manual

158 Troubleshooting
Troubleshooting I/O fencing

How I/O fencing works in different situations

Table C-1 I/O fencing scenarios
Event Node A activity
Both private Races for majority of
networks fail. coordinator disks.
If it wins race for coordinator
disks, Node A ejects Node B
from the shared disks and
continues.
Both private Continues to work.
networks
function again
after event above.
One private Prints message about an
network fails. IOFENCE on the console but
continues.
Node A hangs. Extremely busy for some reason
or is in the kernel debugger.
When Node A is no longer hung
or in the kernel debugger, any
queued writes to the data disks
fail because Node A is ejected.
When Node A receives message
from GAB about being ejected,
it removes itself from the Policy
Master cluster.
Table C-1 describes how I/O fencing works to prevent data corruption in
different situations. The table also includes actions the operator can take in
each situation.
Node B activity
Races for majority of
coordinator disks.
If it loses the race for the
coordinator disks, Node B
removes itself from the Policy
Master cluster.
Crashes. It cannot start the
database because it cannot
write to the data disks.
Prints message about an
IOFENCE on the console but
continues.
Loses heartbeats with Node A,
and races for a majority of
coordinator disks.
Wins race for coordinator disks
and ejects Node A from shared
data disks.
Operator action
When Node B is ejected
from the VCS One cluster,
repair the private
networks, then try to bring
Node B back.
Restore the private
networks and reboot Node
B.
Repair the private
network. After network is
repaired, both systems use
it automatically.
Verify that the private
networks function and
reboot Node A.