Chapter 10. Copy services 563
For example, consider the case of two applications that are independent, yet they are placed
into a single Consistency Group. If an error occurs, synchronization is lost and a background
copy process is required to recover synchronization. While this process is progressing,
MM/GM rejects attempts to enable access to the auxiliary volumes of either application.
If one application finishes its background copy more quickly than the other application,
MM/GM still refuses to grant access to its auxiliary volumes even though it is safe in this case.
The MM/GM policy is to refuse access to the entire Consistency Group if any part of it is
inconsistent.
Stand-alone relationships and Consistency Groups share a common configuration and state
model. All of the relationships in a non-empty Consistency Group have the same state as the
Consistency Group.
10.7.3 Remote copy intercluster communication
In the traditional Fibre Channel, the intercluster communication between systems in a Metro
Mirror and Global Mirror partnership is performed over the SAN. This section describes this
communication path.
For more information about intercluster communication between systems in an IP
partnership, see 10.6.6, “States of IP partnership” on page 556.
Zoning
The IBM Storwize V5000 Gen2 system FC ports on each system must communicate with
each other to create the partnership. Switch zoning is critical to facilitating intercluster
communication.
Intercluster communication channels
When an IBM Spectrum Virtualize system partnership is defined on a pair of systems, the
following intercluster communication channels are established:
A single control channel, which is used to exchange and coordinate configuration
information
I/O channels between each of these nodes in the systems
These channels are maintained and updated as nodes and links appear and disappear from
the fabric, and are repaired to maintain operation where possible. If communication between
the systems is interrupted or lost, an event is logged (and the Metro Mirror and Global Mirror
relationships stop).
Intercluster links
All IBM Storwize V5000 Gen2 node canisters maintain a database of other devices that are
visible on the fabric. This database is updated as devices appear and disappear.
Devices that advertise themselves as IBM SAN Volume Controller or Storwize family product
nodes are categorized according to the system to which they belong. Nodes that belong to
the same system establish communication channels between themselves and begin to
exchange messages to implement clustering and the functional protocols of IBM Spectrum
Virtualize.
Alerts: You can configure the system to raise Simple Network Management Protocol
(SNMP) traps to the enterprise monitoring system to alert on events that indicate an
interruption in internode communication occurred.
To Next Page
Loading...
Need help?
General