HP XP Continuous Access Software - Manual (Page 17)

Continuous Access XP user guide for the XP1024/XP128 17
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 XP1024/XP128 (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 XP1024/XP128 as an MCU can be connected to only one XP1024/XP128 as an
RCU via optical fibre cables. For CU images within one XP1024/XP128, 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.
Initiator ports and RCU target ports
Initiator ports are dedicated Fibre Channel interface ports on the main disk array (MCU) to which RCUs
(RCU target ports) are connected. Initiator ports connect to RCUs to send write I/O operations directly to
RCUs. You can configure Fibre Channel interface ports of the XP1024/XP128 as initiator ports. Use the
Port Change operation (see ” Port change operation ” on page 65) to change the configuration of the
XP1024/XP128 Fibre Channel ports (ordinary target port, initiator port, or RCU target port) as needed.
NOTE: Initiator ports cannot communicate with hosts, but are used exclusively as Continuous Access XP
talkers. Ordinary target ports can be used only for host connect (not for Continuous Access XP).