Software Manual

2.27
Remote Copy Operation
InForm OS Version 2.3.1 Remote Copy User’s Guide
If the primary volume has been previously synchronized, and a resynchronization snapshot
exists, then a fast resynchronization is performed. The two snapshots (the resynchronization
snapshot and the current synchronization snapshot) are compared to determine what changes
have occurred between the creation of each snapshot. The system transmits only these changes
to the secondary volume (Figure 2-17).
Figure 2-17. Fast Resynchronization Using Resynchronization Snapshots
After the entire volume group has been synchronized with the secondary group, the snapshots
that were created on the backup system are deleted, as the base volumes now represent a
valid point-in-time copy. After a resynchronization is complete, the old resynchronization
snapshot is deleted, and the newer snapshot is saved for future resynchronization.
Primary
Storage Server
Primary
Most Recent
Volume Group
Backup
Storage Server
Secondary
Volume Group
Most Recent
Host
I/O might continue
while synchronization
takes place
Snapshots
Snapshots
Previous
(Resynchronization)
Snapshots
Primary system
most recent and
previous snapshots
1
2
compares
Only changes for each volume
are copied over individually
from the most recent snapshot
to the corresponding backup
volume
3
Snapshots on
backup server
are deleted
4
Previous snapshots
on primary server are
deleted and the most
recent snapshots become
resynchronization snapshots
NOTE: Because of the use of multiple snapshots, adequate virtual volume space
must be available. See Remote Copy and Thin Provisioning on page 2.33 for
important information about space allocation and deleted snapshots.