Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

When the network links are restored, attempting to reattach the missing disks to
the disk group on Node 0, or to re-import the entire disk group on either node,
fails. VxVM increments the serial ID in the disk media record of each imported
disk in all the disk group configuration databases on those disks, and also in the
private region of each imported disk. The value that is stored in the configuration
database represents the serial ID that the disk group expects a disk to have. The
serial ID that is stored in a disk’s private region is considered to be its actual value.
VxVM detects the serial split brain when the actual serial ID of the disks that are
being attached mismatches with the serial ID in the disk group configuration
database of the imported disk group.
If some disks went missing from the disk group (due to physical disconnection or
power failure) and those disks were imported by another host, the serial IDs for
the disks in their copies of the configuration database, and also in each disk’s
private region, are updated separately on that host. When the disks are
subsequently re-imported into the original shared disk group, the actual serial
IDs on the disks do not agree with the expected values from the configuration
copies on other disks in the disk group.
Depending on what happened to the different portions of the split disk group,
there are two possibilities for resolving inconsistencies between the configuration
databases:
■ If the other disks in the disk group were not imported on another host, VxVM
resolves the conflicting values of the serial IDs by using the version of the
configuration database from the disk with the greatest value for the updated
ID (shown as update_id in the output from the vxdg list diskgroup
command).
Figure 6-2 shows an example of a serial split brain condition that can be
resolved automatically by VxVM.
245Creating and administering disk groups
Handling conflicting configuration copies