HP StorageWorks Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide (AA-RPHZF-TE, March 2004)

Remote Copy Set Features
35Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide
Figure 10: Remote copy set operation modes
Operation Mode Considerations
Consider the following characteristics when designing your DRM configuration:
■ Synchronous replication is appropriate when exact consistency is critical to the business
application. The application or application recovery depends upon data being written to
both local and remote sites.
■ The greater the Outstanding I/O setting, the more data can be lost when a disaster occurs at
the initiator site. There is no loss of data in synchronous mode.
■ Synchronous operation may deliver best response time for heavy host-write operations. In
most cases, even though synchronous operation must wait for data to be sent to the target
and the target to respond with acknowledgement, it is faster than asynchronous operation
due to overhead in the controller when processing asynchronous commands.
■ Asynchronous operation improves response time for some workloads.
ADD REMOTE_COPY_SETS Command
The ADD REMOTE_COPY_SETS RemoteCopySetName InitiatorUnitName
RemoteNodeName\TargetUnitName command creates a remote copy set and starts a
normalization copy to the target unit. During normalization, the controllers copy all data from
the initiator unit to the target unit.
Outstanding_IO Settings
The OUTSTANDING_IO setting allows you to control the number of outstanding
initiator-to-target writes for a remote copy set. It does not refer to the write queue depth
between the host and the controller. This setting can be applied to both synchronous and
asynchronous remote copy sets. However, this setting causes different behavior, depending on
the remote copy set operation mode.
The default setting is 20 for each remote copy set. There is a shared maximum of 240 available
to all remote copy sets on a controller.
Transaction is not complete
until this point
Perform task
(User)
Update data
(Primary data
center)
Transmit update
(Network)
SYNCHRONOUS
ASYNCHRONOUS
Notify user
(Network)
Update data
(Recovery site)
Perform task
(User)
Update data
(Primary data
center)
Transmit update
(Network)
Update data
(Recovery site)
Time
Time
Recovery site updates
may be done at a later time
Transaction is complete
at this point
CXO7070A
Notify user
(Network)