Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

433Administering sites and remote mirrors
Failure scenarios and recovery procedures
Recovery from a loss of site connectivity
If the network links between the sites are disrupted, the application environments may
continue to run in parallel, and this may lead to inconsistencies between the disk group
configuration copies at the sites. When connectivity between the sites is restored, a serial
split-brain condition may then exist between the sites. One site must be chosen as having
the preferred version of the disk group configuration copies. The configuration copies at
the other sites can then be updated from these copies.
Use the following commands to reattach a site and recover the disk group:
# vxdg -g diskgroup -o overridessb reattachsite sitename
# vxrecover -g diskgroup
In the case that the host systems are configured at a single site with only storage at the
remote sites, the usual resynchronization mechanism of VxVM is used to recover the
remote plexes when the storage comes back on line.
Recovery from host failure
If one or more cluster nodes fail at a site, but the storage remains online, this is handled
either by Serviceguard failover in the case, and by node takeover in the case that the node
was the master for a shared disk group as supported by the Storage Foundation Cluster
File System software.
Recovery from storage failure
If storage fails at a site, the plexes that are configured on that storage are detached locally
if a site-consistent volume still has other mirrors available at the site. The hot-relocation
feature of VxVM will attempt to recreate the failed plexes on other available storage in the
disk group. If no plexes of a site-consistent volume remain in operation at a site, and
hot-relocation cannot recreate the plexes at that site, the site is detached. Because site
connectivity has not been lost, applications running on hosts at the site can still access data
at the other sites. When the storage comes back online, use the following commands to
reattach a site and recover the disk group:
# vxdg -g diskgroup reattachsite sitename
# vxrecover -g diskgroup