HP StorageWorks XP Remote Web Console Software - Manual (Page 14)

Asynchronous Consistency Groups
An XP Continuous Access Asynchronous consistency group is a user-defined set of volume pairs
across which update sequence consistency is maintained and ensured at the remote site. Each pair
must be assigned to a consistency group. XP Continuous Access allows you to configure up to 128
consistency groups (00-7F) for each MCU and provides group-based operations for consistency
groups (for example, split and resync group). Consistency groups enable you to maintain update
sequence consistency for databases which span multiple volumes, allowing immediate database
recovery at the remote site when needed. See
“XP Continuous Access Asynchronous Consistency
Group Operations” (page 29) for further information on XP Continuous Access Asynchronous
consistency group operations.
Remote Copy Connections
The remote copy connections are the physical paths used by the MCUs to communicate with the
RCUs. The number of physical paths in the MCU is limited to eight per logical CU (depending on
the availability of ports). The MCUs and RCUs are connected via Fibre Channel interface cables.
Contact your HP service representative for the latest information on the availability of serial-channel
XP Continuous Access connections.
When Fibre Channel interface (multimode shortwave) connections are used, two switches are
required for distances greater than 0.5 km (1,640 feet). Distances up to 1.5 km (4,920 feet, 0.93
miles) are supported. When Fibre Channel interface (single-mode longwave) connections are used,
two switches are required for distances greater than 10 km (6.2 miles). Distances up to 30 km
(18.6 miles) are supported.
The MCU-to-RCU remote copy configuration (see “Remote Copy Connections” (page 53) ) for XP
Continuous Access Asynchronous has different requirements than the XP Continuous Access
Synchronous configuration, as follows:
•
XP Continuous Access Asynchronous supports 1-to-1 remote copy connections within the same
consistency group. The P-VOLs and S-VOLs of the pairs in a consistency group must be located
within one physical MCU and one physical RCU. This configuration ensures backup integrity
for data that is spread across multiple volumes within one storage system (for example, large
databases).
XP Continuous Access 1-to-n and n-to-1 configurations (n≤4) are valid for XP Continuous
Access Asynchronous, as long as each consistency group does not span local or remote
storage systems.
•
Fibre remote copy supports 1-to-1 remote copy connections. One storage system as an MCU
can be connected to only one storage system as an RCU via optical fibre cables. For the CUs
within one storage system, 1-to-4 and 4-to-1 remote copy connections are supported.
One MCU port (initiator port) can be connected to 64 RCU ports (RCU target ports). One RCU
port can be connected to 16 MCU ports. However, the number of logical paths that can be specified
does not depend on the number of connectable RCU or MCU ports.
HP recommends that you establish at least two independent remote copy connections (one per
cluster) between each MCU and RCU to provide hardware redundancy for this critical
communications path.
When 4,000 pairs or more are used, HP recommends that you restrict the number of pairs when
creating pairs, so that 4,000 pairs or less use one physical path, to distribute load on the physical
path.
To recover the data from a disaster, you must prepare the RCU-MCU paths in addition to the usual
MCU-RCU paths.
14 About XP Continuous Access Operations