 |
» |
|
|
|
The use of Business Continuity Volumes is recommended with
all implementations of MetroCluster/SRDF, and it is required with
M by N configurations, which employ consistency groups. These BCV
devices will provide a good copy of the data when it is necessary
to recover from a rolling disaster—a
second failure that occurs while we are attempting to recover from
the first failure. Protecting against Rolling Disasters | |
An example of a rolling disaster with MetroCluster/SRDF is
as follows. At time T0, all the SRDF links go down. The application
continues to run on the R1 side. At time T1, the SRDF links are
restored, and at T2 a manual resynchronization is started to resync
new data from the R1 to the R2 side. At time T3, while resynchronization
is in progress, the R1 site fails, and the application starts up
on the R2 side. Since the resynchronization did not complete when
there was a failure on the R1 side, the data on the R2 side is corrupt. Using the BCV in Resynchronization | |
In general, you use the business continuity volumes only in
cases where a resynchronization will take place. First, you split
off a consistent copy of the data, then perform the resynchronization,
then re-establish the BCV mirroring. To perform these steps, use
the following sequence of commands: Split the BCV in the secondary Symmetrix
from the mirror group to save a good copy of the data. From node3
or node4: # symmir -g dgoraA split # symmir -g dgoraB split Alternatively, from node1 or node2:# symmir -g dgoraA split -rdf # symmir -g dgoraB split -rdf Resync the data from R1 to R2 devices: # symrdf -cg cgoradb est Use the following command to monitor the status
of the RDF pair state between the R1 and R2 devices: # symrdf -cg cgoradb query Once the column with the "RDF Pair STATE" shows
the state as "Synchronized" for all the devices,
you can proceed to the next step. Re-establish the BCV devices in the secondary Symmetrix
as a mirror of the standard device. From node 3 or node4: # symmir -g dgoraA -full est # symmir -g dgoraB -full est Alternatively, from node1 or node2: # symmir -g dgoraA -full est -rdf # symmir -g dgoraB -full est -rdf
|
Printable version
