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Disaster Scenarios and Their Handling
Chapter 4 95
In this case, initially the
package (P1) is running on node
N1. P1 uses a mirror md0
consisting of S1 (local to node
N1, for example
/dev/hpdev/mylink-sde) and
S2 (local to node N2). The first
failure occurs with all Ethernet
links between the two data
centers failing.
With this failure, the
heartbeat exchange is lost
between N1 and N2. This
results in both nodes trying
to get to the Quorum server.
If N1 accesses the Quorum
server first, the package
continues to run on N1 with
S1 and S2 while N2 is
rebooted. If N2 accesses the
Quorum server, the package
fails over to N2 and starts
running with both S1 and
S2 and N1 is rebooted.
Complete the following steps to
initiate a recovery:
1. You need to only restore the
Ethernet links between the
data centers so that N1 and
N2 can exchange heartbeats
2. After restoring the links, you
must add the node that was
rebooted as part of the cluster.
Run the cmrunnode command
to add the node to the cluster.
NOTE: If this failure is a
precursor to a site failure, and if
the Quorum Service arbitration
selects the site that is likely to
have a failure, it is possible that
the entire cluster will go down.
In this case, initially the
package (P1) is running on node
N1. P1 uses a mirror md0
consisting of S1 (local to node
N1, say
/dev/hpdev/mylink-sde) and
S2 (local to node N2). The first
failure occurs when the
Ethernet links from N1 to the
Ethernet switch in datacenter1
fails.
With this failure, the
heartbeat exchange
between N1 and N2 is lost.
N2 accesses the Quorum
server, as it is the only node
which has access to the
Quorum server. The
package fails over to N2 and
starts running with both S1
and S2 while N1 gets
rebooted.
Complete the following procedure
to initiate a recovery:
1. Restore the Ethernet links
from N1 to the switch in data
center 1.
2. After restoring the links, you
must add the node that was
rebooted as part of the cluster.
Run the cmrunnode command
to add the node to the cluster.
Table 4-1 Disaster Scenarios and Their Handling (Continued)
Disaster Scenario
What Happens When
This Disaster Occurs
Recovery Process