HP StorageWorks XP24000 Continuous Access Software User and Reference Guide, v01 (T5278-96002, June 2007)

Continuous Access supports the basic logical unit (LU) types available on the storage system (for example,
OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L, and OPEN-V). Continuous Access also supports the HP
StorageWorks XP LUNExpansion (LUSE), HPStorageWorksXPVirtual LVI/LUN, and HPStorageWorks
XP
Cache Residency Manager features, ensuring that all user data can be backed up or duplicated. See
“Logical Unit (LU) Types” on page 44 for further information on LU requirements and support.
Continuous Access supports a maximum of 32,768 pairs (entire storage system RCU). When Continuous
Access pairs include size-expanded LUs, the maximum number of pairs decreases. When the HP
StorageWorks XP RAID Manager command device is defined, the maximum number of pairs in the
storage system is 32,7 6 7.
Asynchrono
us Consistency Groups
A Continuous Access Asynchronous consistency group is a user-defined set of volume pairs across which
update
sequ
ence
consistency is maintained and ensured at the remote site. Each pair must be assigned
to a
consist
ency
group. Continuous Access allows you to configure up to 128 consistency groups (00-7F)
for each MC
U
and provides group-based operations for consistency groups (for example, split and resync
group). Co
nsistency groups enable you to maintain update sequ ence consistency for databases which
span multiple
volumes, allowing immed iate database recovery at the remote site when needed. See
“Continuous Access Asynchronous Consistency Group Operations” on page 25 for further information
on 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 lo gical CU (dep ending on the availability
of
ports). The MCUs and RCUs a re connected via Fibre Channel interface cables.
Note: Please contact your HP support representative for the latest information on the availability of
serial-channel 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), and 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 g reater than 10 km (6.2 miles), and distances up to 30 km (18.6 miles)
are s uppor ted. See “Remote Copy Connections” on page 47 for further information on installing and
configuring the FC remote c opy connections.
The MCU-to-RCU remote copy configuration (see “Remote Copy Connections”onpage47) for
Continuous Access Asynchronous has different requirements than the Continuous Access Synchronous
configuration, as follows:
• 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 g roup must be lo cated
within one p hysical MCU and one physical RCU. This config uration ensures backup integrity for
data which is spread across multiple volumes within one storage system (for example, large
databases).
Note: Continuous Access 1-to-n and n-to-1 configurations (n≤4) a re valid for Continuous Access
Asynchronous, as long as each consistency group does not span local or remote storage systems.
• Fibreremotecopysupports1-to-1remotecopyconnections. One storagesystem asanMCU 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 suppor ted.
One MCU port (initiator port) can be connected to 64 RCU ports (RCU target por ts). 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.
Note: HP strongly 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.
16
About
HP StorageWorks XP Continuous Access Software Operations