HP StorageWorks Storage Mirroring Scripting Guide (T2558-96327, April 2009)

7 - 10
Starting replication
Start replication by using the replication start command.
Inserting tasks during replication
Task command processing is a Storage Mirroring feature that allows you to insert and run tasks at
various points during the replication of data. Because the tasks are user-defined, you can achieve a
wide variety of goals with this feature. For example, you might insert a task to create a snapshot or
run a backup on the target after a certain segment of data from the source has been applied on the
target. This allows you to coordinate a point-in-time backup with real-time replication.
Task command processing can be enabled from the Management Console, but it can only be initiated
through a scripting command.
If you disable this option on a source server, you can still submit tasks to be processed on a target,
although task command processing must be enabled on the target.
Because Storage Mirroring replication follows the same write sequence within and across multiple
files, it provides complete data integrity at all times. At any given moment, the target represents a
single point in time from the source, which makes the target crash consistent. But for some
applications, crash consistency may not be adequate. You may require that the source data be in a
quiescent (latent) state, similar to an application checkpoint. You need to be able to identify when
the application is stable, which is usually when all of the data has been written to disk. This can be
triggered by stopping the service. With task command processing, you can stop the source service
just long enough to identify that stopped point in time as a stable state, insert a task at that point
into the Storage Mirroring replication queue to trigger a backup or snapshot on the target, and then
restart the service. Here is how the process would work.
1. Storage Mirroring and an application are both running on the source. Only Storage Mirroring is
running on the target.
2. The application data is changing on the source and Storage Mirroring is capturing those data
changes and transmitting them to the target.
3. A script is launched (either manually or perhaps scheduled by the Windows Scheduler) that
stops the application service on the source, pauses to give the service time to shutdown and
write the data to disk, initiates a Storage Mirroring task command, and then restarts the
application service on the source.
4. The Storage Mirroring task command is transmitted, inline with the source replication data, to
the target.
Command REPLICATION START
Description Initiates the replication process
Syntax
REPLICATION START <conid | *> [CLEARRESTOREREQUIRED]
Options
 conid—Connection ID assigned to the source/target connection
 *—Specifies all connection IDs
 CLEARRESTOREREQUIRED—Clears the restore required flag and
initiates replication
Examples
 replication start 1
 replication start *