Veritas Storage Foundation 5.1 SP1 Cluster File System Administrator"s Guide (5900-1738, April 2011)
Table 2-2
I/O fencing scenarios (continued)
Operator actionNode B: What
happens?
Node A: What
happens?
Event
Power on the failed
disk array so that
subsequent network
partition does not
cause cluster
shutdown, or replace
coordinator disks.
See “Replacing I/O
fencing coordinator
disks when the
cluster is online”
on page 88.
Node B has left the
cluster.
Node A continues to
operate in the
cluster.
The disk array
containing two of the
three coordinator
disks is powered off.
Node B gracefully
leaves the cluster and
the disk array is still
powered off. Graceful
leave implies a clean
shutdown so that
vxfen is properly
unconfigured.
Power on the failed
disk array and restart
I/O fencing driver to
enable Node A to
register with all
coordinator disks, or
replace coordinator
disks.
See “Replacing
defective disks when
the cluster is offline”
on page 182.
Node B has left
cluster due to crash
or network partition.
Node A races for a
majority of
coordinator disks.
Node A fails because
only one of the three
coordinator disks is
available. Node A
panics and removes
itself from the
cluster.
The disk array
containing two of the
three coordinator
disks is powered off.
Node B abruptly
crashes or a network
partition occurs
between node A and
node B, and the disk
array is still powered
off.
About server-based I/O fencing
In a disk-based I/O fencing implementation, the vxfen driver handles various
SCSI-3 PR based arbitration operations completely within the driver. I/O fencing
also provides a framework referred to as customized fencing wherein arbitration
operations are implemented in custom scripts. The vxfen driver invokes the
custom scripts.
The CP server-based coordination point uses a customized fencing framework.
Note that SCSI-3 PR based fencing arbitration can also be enabled using customized
fencing framework. This allows the user to specify a combination of SCSI-3 LUNs
and CP servers as coordination points using customized fencing. Customized
fencing can be enabled by specifying vxfen_mode=customized and
vxfen_mechanism=cps in the /etc/vxfenmode file.
43Storage Foundation Cluster File System architecture
About I/O fencing