HP serviceguard t2808-90006 manual Dev/hpdev/mylink-sdf

			Disaster Scenarios and Their Handling
Table 4-1	Disaster Scenarios and Their Handling (Continued)
Disaster Scenario		What Happens When	Recovery Process
		This Disaster Occurs
This is a multiple failure		The package (P1) continues	For the first failure scenario,
scenario where the failures		to run on N1 after the first	complete the following procedure
occur in a particular sequence in		failure, with md0 consisting	to initiate a recovery:
the configuration that		of only S1.	1. Restore the links in both
corresponds to figure 2 where		After the second failure, the
Ethernet and FC links do not go			directions between the data
		package (P1) fails over to
over DWDM.			centers. As a result, S2
		N2 and starts with S1.
			(/dev/hpdev/mylink-sdf) is
The package (P1) is running on		Since S2 is also accessible,
			accessible from N1 and S1 is
a node (N1). P1 uses a mirror		the extended distance
			accessible from N2.
md0 consisting of S1 (local to		cluster adds S2 and starts
			2. Run the following commands
node N1, say /dev/hpdev/		re-mirroring of S2.
mylink-sde) and S2 (local to			to remove and add S2 to md0
node N2).			on N1:
The first failure occurs with all			# mdadm --remove /dev/md0
FC links between the two data			/dev/hpdev/mylink-sdf
centers failing, causing N1 to			# mdadm --add /dev/md0
lose access to S2 and N2 to lose
			/dev/hpdev/mylink-sdf
access to S1.
After recovery for the first			The re-mirroring process is
			initiated. The re-mirroring process
failure has been initiated, the
			starts from the beginning on N2
second failure occurs when
			after the second failure. When it
re-mirroring is in progress and
			completes, the extended distance
N1 goes down.
			cluster detects S2 and accepts it as
			part of md0 again.

Chapter 4 89