Site consistency means that at any point in time, the data at each site is consistent with the application for a given set of volumes. A site-consistent volume must have at least one plex, or mirror, on each configured site in the disk group. The site consistency is ensured by detaching a site when a site-consistent volume loses its last complete plex on that site. The site detach detaches all the plexes on that site and also disallows further configuration updates to the configuration copies on that site. Turn on this behavior by setting the siteconsistent attribute to on on the desired volumes.
The siteconsistent attribute is also present at the disk group level and can be used to turn on or off the site consistency functionality in the disk group boundary. In addition, if you turn on the siteconsistent attribute for a disk group, each new volume created in the disk group inherits the site consistency of the disk group, by default. Setting the siteconsistent attribute on a disk group does not affect siteconsistent attributes for existing volumes. You can also control the site consistency on individual volumes.
By default, creating a site-consistent volume also creates an associated version 20 DCO volume, and enables Persistent FastResync on the volume. This allows faster recovery of the volume during the reattachment of a site.
Before setting site consistency on a disk group, be sure to meet the following requirements: