HP StorageWorks Continuous Access XP user guide for the XP10000/XP12000 (December 2005)

Continuous Access XP user guide for the XP10000/XP12000 17
XP Async volume pair must be assigned to a consistency group. Continuous Access XP can configure up to
128 consistency groups (0-7F) for each MCU and provides group-based operations for consistency groups
(for example, split and resync group). Use consistency groups to maintain update sequence consistency for
databases spanning multiple volumes, allowing immediate database recovery at the remote site when
needed. See ”Continuous Access XP Asynchronous consistency group operations” on page 23 for further
information.
Only Continuous Access XP Asynchronous pairs belonging to the same CLPR can be allocated to one
Continuous Access XP consistency group. For more information about CLPRs, see the HP StorageWorks XP
Disk/Cache Partition User Guide.
Remote copy connections
Remote copy connections are physical paths MCUs use to communicate with RCUs. The number of
physical paths in the MCU is limited to eight per logical CU image. MCUs and RCUs are connected via
Fibre Channel interface or serial (ESCON) interface cables.
• When Fibre Channel interface connections are used, 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 with dual switches
utilizing shortwave connections. Distances up to 10 km (6.2 miles) are supported using dual switches
with longwave connections. Distances up to 30 km (18.6 miles) are supported using dual switches with
longhaul connections. Distances up to 100 km are supported by using dual switches with DWDM. See
”Fibre Channel remote copy connections” on page 34 for further information about installing and
configuring Fibre Channel remote copy connections.
• When serial interface connections are used, ESCON directors (ESCDs) and/or ESCON repeaters are
required for distances greater than 3 km (1.9 miles). Continuous Access XP operations can be
performed at distances of up to 43 km (26.7 miles) using standard ESCON support. Long-distance
solutions are provided, based on user requirements and workload characteristics, using approved
protocol converters and communication lines, such as T1/T3/ATM. See ”Serial remote copy
connections” on page 35 for further information about installing and configuring serial remote copy
connections.
The MCU-to-RCU remote copy configuration for Continuous Access XP Asynchronous has different
requirements than the Continuous Access XP Synchronous configuration, as follows:
• Continuous Access XP Synchronous supports 1-to-n and n-to-1 remote copy connections (n≤4). One
MCU can be connected to as many as four RCUs. One RCU can be connected to as many as four
MCUs (one MCU/RCU = one physical CU, including all sixteen CU images).
• Continuous Access XP Asynchronous supports 1-to-1 remote copy connections within the same
consistency group. P-VOLs and S-VOLs of pairs in a consistency group must be within one physical
MCU and one physical RCU. This configuration ensures backup integrity for a data set spread across
multiple volumes within one XP10000/XP12000 (such as large databases).
Continuous Access XP Asynchronous 1-to-n and n-to-1 (n ≤4) configurations (one main disk array and
multiple remote disk arrays) are valid for Continuous Access XP Asynchronous if all volumes belonging
to a single consistency group are only 1-to-1.
• With direct connect Fibre Channel (no switch), fibre remote copy supports 1-to-1 remote copy
connections. One XP10000/XP12000 as an MCU can be connected to only one XP10000/XP12000
as an RCU via optical fibre cables. For CU images within one XP10000/XP12000, 1-to-4 and 4-to-1
remote copy connections are supported via direct connects or an FC switch.
HP strongly recommends 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.
NOTE: To recover data from a disaster, prepare the RCU-MCU paths in addition to the usual MCU-RCU
paths. For more information, see ”Registering RCUs (Add RCU)” on page 64.
When you set the RCU-MCU path, you must also specify:
• The same combination of CU images as when you set the MCU-RCU path if you set the MCU-RCU path
and specify the CU image.