IBM System Storage DS3000 Programming Manual page 463

v VLAN – Both local and remote systems must have the same VLAN setting in order to communicate
v iSCSI listening port
v Jumbo Frames
v Ethernet Priority
Enhanced Global Mirror Groups
Some applications, such as file systems and databases, distribute data storage across many logical drives.
To create a failover site for such applications, all of the application data logical drives must be replicated
on a storage subsystem at a remote site. The synchronization between the original data logical drives and
the replicated data logical drives must be coordinated so that writes on the local storage subsystem are
accurately reflected on the remote storage subsystem. The purpose of an Enhanced Global Mirror Group
is to associate a set of logical drives so that mirror synchronization can be coordinated for the logical
drive set, creating a consistent data set on the remote storage system.
v The local storage subsystem is the primary side of the Enhanced Global mirror group. The remote
storage subsystem is the secondary side of the Enhanced Global Mirror Group.
v All logical drives added to the Enhanced Global Mirror Group on the local storage subsystem hold the
primary role in the mirrored relationship.
v All logical drives added to the Enhanced Global Mirror Group on the remote storage subsystem hold
the secondary role in the mirrored relationship.
During the synchronization, point-in-time images for all primary logical drives are created at the same
time. Data is replicated for all logical drives in the group to the remote system within the same
synchronization interval. The synchronization progress for a given resynchronization operation varies
among member logical drives. However, point-in-time images of the Secondary logical drives at the
completion of data synchronization are created at the same time after all members of the group have
completed the synchronization. If resynchronization fails (even due to just one member), prior consistent
images remain on the Secondary AMG to preserve the last known consistent data.
The properties associated with the Enhanced Global Mirror Group include the following:
v World Wide Name
v User label
v Role: primary or secondary
Note: The role is an Enhanced Global Mirror Group attribute, not a mirrored logical drive attribute. Role
reversal affects all logical drives in the Enhanced Global Mirror Group.
v Mirrored I/O Channel Type: Fibre Channel or iSCSI
v Timestamp of the last known recovery point
v Resynchronization interval
Resynchronization interval is the amount of time between automatically sending updates of modified
data from the primary storage subsystem to the secondary storage subsystem. The interval, expressed in
minutes, represents the time between the starting points of sending updates from the primary to the
secondary. A resynchronization interval of zero means that synchronization is manual.
v Synchronization progress: The synchronization progress is the percent complete and an estimated time
to completion of the current synchronization activity if in progress.
v Alert threshold for resynchronization completion time (for example, alert if the resynchronization takes
too long)
v Alert threshold for recovery point degradation (such as, age of the Secondary PiTs)
v Repository utilization warning threshold
v Member logical drive list
Chapter 7. About Enhanced Global Mirroring premium feature
7-3