Two-site partnerships replicate volume data that is on one system
to a remote system. Two-site partnerships are required for policy-based
replication. Partnerships can be used for migration, 3-site replication, and disaster
recovery situations.
Both policy-based replication and remote-copy function use partnerships for creating copies in recovery
system. Policy-based replication currently supports asynchronous,
2-site replication.
Before you can
configure policy-based replication or configure remote-copy objects, a partnership
between all the systems must be established. If relationships or consistency
groups exist between different systems, those systems must maintain their partnership. Each system
can maintain up to three partnerships. The system can either support maximum
of three IP partnerships, three Fibre Channel partnership, or combination of these two type of
partnerships. As many as four systems can be directly associated with each other.
Systems also become indirectly associated with each other through partnerships. If
two systems each have a partnership with a third system, those two systems are indirectly
associated. A maximum of four systems can be directly or indirectly associated.
The state of the partnership helps determine whether the partnership operates as
expected. A partnership can have the following states:
Configured
Both the local and remote systems have a partnership that is defined and are running as
expected.
Partial Local
For the partnership to be fully configured, you must create a partnership from the remote system
to the local system. The system supports both Fibre Channel and IP
connections between partnered systems. Use the
management GUI to configure partnerships or use the mkfcpartnership for Fibre
Channel connections or the mkippartnership for IP connections.
Local Stopped
Indicates that the partnership is defined on both the systems, but the partnership is stopped on
the local system.
Remote Stopped
Indicates that the partnership is the defined on both the systems, but the partnership is
stopped on remote system.
Partial Local Stopped
Indicates that only the local system has the partnership that is defined and the partnership is
stopped on the local system.
Local Excluded
Indicates that both the local system and the remote system have the partnership that is defined,
but the local system is excluding the link to the remote system. This state usually occurs when the
link between the two systems is compromised by too many errors or slow response times of the
partnership.
Remote Excluded
Indicates that both the local system and the remote system are defined in a partnership, but the
remote system is excluding the link to the local system. This state usually occurs when the link
between the two systems is compromised by too many errors or slow response times of the
partnership.
Exceeded
Indicates that the partnership is unavailable because the network of systems exceeds the number
of systems that are allowed in partnerships. To resolve this error, reduce the number of systems
that are in partnerships in this network.
Not Present
Indicates that the remote system is not visible. This state can be caused by a problem with the
connectivity between the local and remote system or if the remote system is unavailable.
The following examples show possible Fibre Channel
partnerships that can be established among the systems.
Figure 1 depicts two systems
that are not in a partnership.Figure 1. Two systems with no partnerships
Figure 2 depicts two systems with
one Fibre Channel partnership.Figure 2. Two systems with one Fibre Channel partnership
Figure 3 depicts four systems in
a Fibre Channel partnership. System A might be a disaster recovery site.Figure 3. Four systems in a Fibre Channel partnership
Figure 4 depicts three systems in
a migration situation. Data Center B is migrating to C. System A is host production, and System B
and System C are disaster recovery.Figure 4. Three systems in a migration situation
Figure 5 depicts systems that are
in a fully connected mesh configuration. Every system has a partnership to each of the three other
systems.Figure 5. Systems in a fully connected mesh configuration
Figure 6 depicts four systems in
three Fibre Channel partnerships.Figure 6. Four systems in three Fibre Channel partnerships
Figure 7 depicts a system
configuration that is not supported. Five systems are in the connected set, even though no
individual system is in more than two Fibre Channel partnerships.Figure 7. An unsupported system configuration
The following examples show Fibre Channel and IP
partnerships that can be established with the systems. For more information about configuring and
deploying systems with IP partnerships, see IP partnership configuration.
Figure 8 depicts two systems
with no partnerships.Figure 8. Two systems with no partnerships
Figure 9 depicts two systems
with one Fibre Channel or IP partnership.Figure 9. Two systems with one Fibre Channel or IP partnership
Figure 10 depicts four systems in
a partnership. System D might be a disaster recovery site.Figure 10. Four systems with either one Fibre Channel partnership or one IP partnership.
Figure 11 depicts three systems
and three partnerships.Figure 11. Three systems with two Fibre Channel partnerships and one IP partnership.
Figure 12 depicts systems that
are in a fully connected mesh configuration. Every system has a Fibre Channel or IP partnership to
each of the three other systems.Figure 12. Four systems in a fully connected mesh configuration.
Figure 13 depicts four systems in
three partnerships.Figure 13. Four systems with one Fibre Channel partnership and two IP partnerships
Figure 14 depicts systems that are
in a fully connected mesh configuration. Every system has IP partnerships to each of the three other
systems.
Figure 14. Four systems in a fully connected mesh configuration with multiple
IP partnership
Figure 15 depicts four systems in a
partnership with multiple IP partnership. System D might be a disaster recovery site.
Figure 15. Four systems with one Fibre Channel partnership or multiple IP
partnership
Figure 16
depicts three systems and three partnerships.
Figure 16. Three systems with one Fibre Channel partnerships and two IP
partnership
Figure 17 depicts a system
configuration that is not supported. Five systems are in the connected set, even though no
individual system is in more than two Fibre Channel or IP partnerships.Figure 17. An unsupported system configuration
To establish a partnership between two systems that are
connected through Fibre Channel connections, you must run the mkfcpartnership
command from both systems. For example, to establish a partnership between system A and system B,
you must run the mkfcpartnership command from system A and specify system B as
the remote system. The partnership is then partially configured and is sometimes described as
one-way communication. Next, you must run the mkfcpartnership command from system
B and specify system A as the remote system. When this command completes, the partnership is fully
configured for two-way communication between the systems. If the local and remote system uses IP
connections, you need to enter the mkippartnership command on both the local and
remote system to fully configure the partnership. You can also use the management GUI to create partnerships.
Portsets replace the
requirement for creating groups for IP partnerships. Dedicated portsets can be
created for remote copy traffic. The dedicated portsets provide group of IP addresses for IP
Partnerships. Each node can have one IP address that is assigned to a portset for
traffic. If the local system in the IP partnership contains four nodes, a portset
can be created that defines four IP addresses, one per each node. Similarly, the remote system with
four nodes, a portset on that system can also have four IP addresses to handle
traffic exclusively. During updates of the software, any IP addresses that are assigned to
groups with an existing IP partnership are automatically moved to a corresponding
portset. For example, if group 1 is defined on the system before the update then
IP addresses from that remote-copy group are mapped to portset 1 after the update. Similarly, IP
address in group 2 is mapped to portset 2. Before you can configure a new IP
partnership, you need to define a portset and assign IP addresses to nodes.
You can configure portsets so that each IP
partnership can be mapped to two portsets, one for each WAN link between systems. For network
configurations that have a single link between systems in an IP partnership, a single portset can be
defined in the Portset Link 1 field on the Create
Partnership page from GUI. You can also use the
-link1 attribute in the mkippartnership command for
partnerships with a single link. For a partnership with dual links, a second portset must be
mapped defined in the Portset Link 2 field. Use the
-link2 attribute to specify the second portset for a dual link
configuration.
Background copy management
Note: Background copy management is not applicable for policy-based
replication.
In a multiple-cycling Global Mirror copy, the
linkbandwidthmbits parameter of the mkfcpartnership and
mkippartnership commands controls the rate at which updates are propagated to the
remote system. To ensure that the
remote copies are as similar as possible to the local copies, the bandwidth parameter needs to be at
least the average rate that write operations are applied to all volumes that are replicated by using
multiple-cycling Global Mirror
across this partnership. For optimum
Recovery Point Objective
(RPO), keep the bandwidth parameter less than the actual available bandwidth to ensure that
multiple-cycling Global Mirror
relationships do not congest the fabric. Also, leave sufficient bandwidth for Metro Mirror and noncycling Global Mirror relationships to support the
I/O that are being replicated.
Replication between IBM Spectrum Virtualize
systems
Systems that run IBM Spectrum Virtualize software
are in one of two layers: the replication layer or the storage layer.
A SAN Volume Controller system is always
in the replication layer.
A FlashSystem family
system is in the storage layer by default, but the system can be configured to be in the replication
layer instead.
To create a partnership between systems, both systems must be in the same layer.
You can change layer of IBM Spectrum Virtualize
systems. For more information, see System layers.Figure 18. Example configuration with systems in different layers