HP Veritas Volume Manager 5.0 -UX 11i v3 vxdg, vxdg, seqno, Disk A, Disk A, Disk B, Actual A, Actual B, Actual A, database, Actual B, database, vxdg list, Expected A, Expected A, Expected B

Creating and administering disk groups 193

Handling conflicting configuration copies

■If the other disks were also imported on another host, no disk can be considered to have a definitive copy of the configuration database. The figure below illustrates how this condition can arise for two disks.

Figure 4-3	Example of a true serial split brain condition that cannot be resolved
	automatically

	Partial disk group			Partial disk group
imported on host X			imported on host Y
		Disk A			Disk B
		Actual A = 1			Actual B = 1
		Configuration			Configuration
		database			database
		Expected A = 1			Expected A = 0
		Expected B = 0			Expected B = 1

1.Disks A and B are imported independently on separate hosts. The actual and expected serial IDs are updated independently on each disk.

Shared disk group fails to import

Disk A

Actual A = 1

Configuration

database

Expected A = 1 Expected B = 0

Disk B

Actual B = 1

Configuration

database

Expected A = 0 Expected B = 1

2.The disk group cannot be reimported on the cluster. This is because the databases do not agree on the actual and expected serial IDs. You must choose which configuration database to use.

This is a true serial split brain condition, which VxVM cannot correct automatically. In this case, the disk group import fails, and the vxdg utility outputs error messages similar to the following before exiting:

VxVM vxconfigd NOTICE V-5-0-33 Split Brain. da id is 0.1, while dm id is 0.0 for DM mydg01

VxVM vxdg ERROR V-5-1-587 Disk group newdg: import failed: Serial Split Brain detected. Run vxsplitlines

The import does not succeed even if you specify the -fflag to vxdg. Although it is usually possible to resolve this conflict by choosing the version of the configuration database with the highest valued configuration ID (shown as the value of seqno in the output from the vxdg list diskgroup grep config command), this may not be the correct thing to do in all circumstances.