Data Path; Consistency Groups; Interfaces - HP StorageWorks P9000 User Manual

During normal operations, the P-VOL remains available to the host for read and write I/O operations.
The secondary system rejects write I/Os for the S-VOL, unless the write-enable option is specified
for the S-VOL. Then, write I/O is allowed to the S-VOL while the pair is split. In this instance, S-VOL
and P-VOL track maps keep track of differential data and are used to resynchronize the pair.
Logical units on the local and remote systems must be defined and formatted prior to pairing.

Data path

Continuous Access Synchronous operations are carried out between local and remote systems
connected by a Fibre Channel interface. The data path, also referred to as the remote copy
connection, connects ports on the local P9500 system to the ports on the remote system. The ports
are assigned attributes that allow them to send and receive data.
One data path connection is required, but two or more independent connections are recommended
for hardware redundancy. A maximum of eight paths per control unit (CU) can be used.

Consistency groups

A consistency group is a set of volume pairs that are in the same primary and secondary systems,
on which copy operations are performed simultaneously, and in which the pairs' status remains
consistent.
When you issue a command, it is executed on all pairs in the group. The pairs' status changes at
the same time, depending on group options.
Although consistency is a primary function of a group, certain operations take priority. For example,
if the PSUS command is issued to a consistency group in which one of the pairs is in the process
of being updated, the pair is not PSUS immediately, as all of the other pairs are. The pair is PSUS
only when the update operation is complete. This allows data integrity to be maintained between
P-VOLs and S-VOLs. The same behavior occurs for a suspend operation caused by a system failure.
Continuous Access Synchronous operations can be performed on pairs in a maximum of 128
consistency groups on the primary system.

Interfaces

You perform Continuous Access Synchronous operations using of the following interfaces:
Remote Web Console, a browser-based interface from which Continuous Access Synchronous
can be setup, operated, and monitored. The GUI provides the simplest method for performing
operations, requiring no previous experience.
◦ The primary system must be LAN-attached to a Remote Web Console computer.
◦ The secondary system should also be LAN-attached to a separate Remote Web Console
at the remote site. This allows you to perform operations more efficiently on the secondary
system in the event that the main site is not available.
RAID Manager is a command line interface used to display pair information and perform all
copying and pair-managing operations. RAID Manager provides a full scripting capability
which can be used to automate replication operations. RAID Manager is required for performing
failover operations.
10 Continuous Access Synchronous overview