HP StorageWorks XP24000 Continuous Access Software User and Reference Guide, v01 (T5278-96002, June 2007)
To provide greater flexibility and to enable the storage system to be tailored to unique customer operating
requirements, additional operational parameters, or optional modes, are available for the storage
system. At installation, the storage system modes are set to their d efault values, so make sure to d iscuss
these settings with your HP service representative. The storage system m od es can only be changed by
your HP service representative.
Note
: No storage system mode for Continuous Access is supported for now. This information was
current at the time of publication of this document, but it may change. Please contact your HP service
representative for the latest storage system mode information.
Main and Remote Control Units (MCUs and RCUs)
The main control unit (MCU) and rem ote control u n it (RCU) control Continuous Access operations:
• The MCU is the c ontrol unit in the primary storage system which controls the P-VOLs of the
Continuous
Access pairs. The Remote We b Console computer must be LAN-attached to the MCU
of each Continuous Access pair. The MCU communicates with the RCU via the dedicated remote
copy connections. The MCU controls the host I/O operations to the Continuous Access P-VOLs as
well as the
Continuous Access initial copy and remote copy operations between the P-VOLs and
S-VOLs. The MCU also manages the Continuous Access pair status and configuration information.
• The RCU is the CU in the remote storage system which controls the S-VOLs of the Continuous
Access pairs. The RCU assists in managing the Continuous Access pair status and configuration
(for e xample, rejects write I/Os to Continuous Access S-VOLs). The RCU executes the remote
copy oper
ations issued by the MCU. The second ary Remote Web Console comp uter should be
attached to the RCUsatthe remotesiteonaseparate LAN. The RCUsshouldalsobeattachedto
a
host system to a llow sense information to be reported in case of a problem with a secondary
volume o
r
remote storage system and to provide disaster recovery capabilities.
You can d
efine the MCU and RCU whether or not you specify the CU. To define the MCU and
RCU when specif ying the CU, specif y the desired CU. To define the MCU and RCU when not
specifying the CU, specify CU Free. For more information on how to define the MCU and RCU, see
“Adding an RCU” on page 71.
Thestorage system CU canfunctionsimultaneouslyasanMCU forone or more P-VOLs andasanRCU
for one or more S-VOLs, provided the remote copy connections and Fibre Channel ports are properly
config
ured. The storage system provides two logical disk controllers (LDKCs). Each LDKC provides up
to
255
logical CUs (00-FE), with each CU controlling u p to 256 logical devices (LDEVs). To define the
MCU
an
d
RCU when specifying the CU, the Continuous Access soft ware allows you to select the desired
CU
in
the
connected MCU and specify the desired CU in the RCU.
Continuous Access operations can be performed on all LDEVs except for the storage system command
device. For further information on the storage system comm a nd device, see the HP StorageWorks XP
RAID Manager User’s Guide.
Note:
This document provides instructions for performing Continuous Access operations with HP
XP24000 Disk Arrays as the MCUs. If you are using non-HP XP24000 Disk Arrays as MCUs, use the
HP StorageWorks XP24000 Continuous Access Software User and Reference Guide for the non-storage
sys
tem models.
Pairs (P-VOLs and S-VOLs)
Continuous Access performs remote copy operations for pairs created by the user. Each Continuous
Access pair consists of one primary volume (P-VOL) and one secondary volume (S-VOL), which can be
located in different storage systems. The Continuous Access P-VOLs a re the primary volumes (LUs) which
contain the original data, and the Continuous Access S-VOLs are the secondary o r mirrored volumes
(LUs) which contain the b ackup or duplicate data. The primary and secondary volumes must have the
same format and capacity (and a SCSI path definition is required).
During normal Continuous Access operations, the P-VO L remains available to all hosts at all times
for read and write I/O o perations. During normal Continuous Access operations, the RCU rejects all
host-requested write I/Os for the S-VOLs. The S-VOL write enable option allows write access to an S-VOL
while the pair is split and uses the S-VOL and P-VOL differential data to resynchronize the pair (see
“S-VO L Write Option” on page 20).
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