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Configuring replication
23 Dell EMC SC Series: VMware Site Recovery Manager Best Practices | 2007-M-BP-V
5.6 Data consistency while replicating the active snapshot
Figure 7 and the steps that follow describe the consistency states of replications during plan execution while
replicating the active snapshot.
Consistency states of active snapshot replications during plan execution
1. As writes are committed to the source volume, they are almost simultaneously transferred to the
destination and stored in the active snapshot. Consistent snapshots can still be taken of the source
volume, and the check points are transferred to the destination volume when replicating the active
snapshot.
2. During a recovery plan test, a new snapshot is taken of the destination volume that locks in all the
data transferred up to that point. Data stored within the active snapshot is most likely crash
consistent. For example, in Figure 7:
a. Although the 3:00 p.m. primary site snapshot was application consistent at the time of the SRM
recovery snapshot, the data must still be deemed crash consistent because it is highly probable
that writes into the active snapshot occurred after the 3:00 p.m. snapshot was taken.
b. If the application is unable to recover the crash consistent data captured in this snapshot, then
manual steps are required in order to present the last known consistent snapshot to the host
(such as the 3:00 p.m. frozen snapshot).
c. The only time that application data can be considered consistent while replicating the active
snapshot is if all I/O has ceased to the source volume, followed by a complete synchronization of
the data from the source to the destination.