VERITAS Volume Manager 3.1 Administrator's Guide

Cluster Functionality
FastResync (Fast Mirror Resynchronization)
Chapter 7314
FastResync (Fast Mirror Resynchronization)
NOTE You may need an additional license to use this feature.
The FastResync feature (also called Fast Mirror Resynchronization,
which is abbreviated as FMR) is supported for shared volumes. The
update maps (FMR maps) are distributed across in the cluster. The
existence of non-persistent maps is less moot in a cluster environment
because only one node in the cluster must be up for the FMR maps to be
available. A single node crash does not cause the loss of FMR maps.
Since the region size must be the same on all nodes in a cluster for a
shared volume, the value of the vol_fmr_logsz tunable on the master
overrides the tunable values on the slaves, if the slave values are
different. Because the value of a shared volume can change, the
vol_fmr_logsz tunable value is retained for the life of the volume or
until FastResync is turned on for the volume.
The map updates are applied under the auspices of the master node.
When the master node distributes updates to all nodes, all updates are
applied either to all nodes or to none of the nodes. The master node
orchestrates a two-phase commitment for applying any updates. See
Figure 7-2, Bitmap Clusterization,.