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442 Administering 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.
You can 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 VCS failover in the case of the Storage Foundation HA
product, or 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
Failure of storage at a site. See “Recovery from storage failure” on
page 442.
Failure of both hosts and storage at a site. See “Recovery from site failure” on
page 443.
Failure scenario Recovery technique