HP StorageWorks XP Remote Web Console Software - Manual (Page 14)

Data Volume Pair
URz performs remote copy operations for data volume pairs created by the user. Each URz pair
consists of one primary data volume and one secondary data volume which can be located in
different storage systems. The URz primary data volumes are the primary volumes (LDEVs) which
contain the original data, and the URz secondary data volumes are the secondary volumes (LDEVs)
which contain the backup or duplicate data. During normal URz operations, the primary data
volume remains available to all hosts at all times for read and write I/O operations. During normal
URz operations, the secondary storage system rejects all host-requested write I/Os for the secondary
data volume. The secondary data volume write enable option allows write access to a secondary
data volume while the pair is split and uses the secondary data volume and primary data volume
track maps to resynchronize the pair (see
Secondary Data Volume Write Option ).
URz also supports the Virtual LVI/LUN (VLL) and XP Cache LUN features, so that URz meets a
variety of user needs and facilitates data copying and data migration. This ensures that all user
data can be backed up or duplicated. See
Duplicate VOLSER (Volume Serial Number) for further
information on LU requirements and support.
Journal Volume
When URz is used, updates to primary data volumes can be stored in other volumes, which are
called journal volumes. The updates (which are sometimes referred to as update data) that will be
stored in journal volumes are called journal data.
Because journal data will be stored in journal volumes, you can perform and manage highly
reliable remote copy operations without suspension of remote copy operations. For example:
Even if a communication path between the primary storage system and the secondary storage
system fails temporarily, remote copy operations can continue after the communication path is
recovered.
If data transfer from hosts to the primary storage system is temporarily faster than data transfer
between the primary storage system and the secondary storage system, remote copy operations
between the primary storage system and the secondary storage system can continue. Because
journal volumes can contain a lot more update data than the cache memory can contain, remote
copy operations can continue if data transfer from hosts to the primary storage system is faster for
a relatively long period of time than data transfer between the primary storage system and the
secondary storage system.
The Number of Journal Volumes
One journal group can contain up to 16 journal volumes. Each of the journal volumes can have
different volume sizes and different RAID configurations. Journal data will be stored sequentially
and separately into each journal volume in the same journal group.
Specifications of Journal Volumes
•
Types of logical units (LUs):
The following DKU emulation types are allowed for journal volumes:
Table 2 Emulation Types for Journal Volumes
Supported Emulation Types Emulation Category
◦ OPEN-V
◦ All mainframe volumes that can be used with XP disk array
NOTE: Status of mainframe volumes cannot be referenced.
DKU (drive)
•
Volumes and their capacity:
You can use VLL volumes for journal volumes.
14 Overview of Universal Replicator for Mainframe Operations