Partnerships

Partnerships can be used to create a disaster recovery environment or to migrate data between systems that are in different locations. Partnerships define an association between a local system and a partner system.

Before a Metro Mirror or Global Mirror relationship or consistency group can be created with a remote system, a partnership between the two systems must be established. If Global Mirror or Metro Mirror relationships or consistency groups exist between two remote systems, those systems must maintain their partnership. Each system can maintain up to three partnerships, and each partnership can be with a single partner system. 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 nodes within the system must know not only about the relationship between the two volumes but also about an association among systems.

To establish a partnership between two systems, you must create the partnership using the Create Partnership dialog on both systems. For example, to establish a partnership between system A and system B, run the dialog from system A and specify system B as the partner system. At this point, the partnership is partially configured and is sometimes described as one-way communication. Next, run the dialog on system B and specify system A as the partner system. When this operation completes, the partnership is fully configured for two-way communication between the systems.

The state of the partnership helps determine whether the partnership operates as expected. A system partnership can have the following states:

Partially Configured: Local (partially_configured_local): Indicates that only the local system has the partnership defined. For the displayed system to be fully configured and to complete the partnership, you must define the system partnership from the system that is displayed to this system. Run the mkfcpartnership command for Fibre Channel connections, run the mkippartnership command for IP connections, or use the management GUI on the remote system.
Fully Configured (fully_configured): Indicates that the partnership is active on the local and remote system and is started.
Not Present (not_present): Indicates the remote system is not visible. This could be caused by a problem with the connectivity between the local and remote system or by the remote system being inactive.
Partially Configured: Local Stopped (partially_configured_local_stopped): Indicates that only the local system has the partnership defined, and the partnership has been stopped on the local system.
Note: It is the partnership that is stopped, not the system.
Fully Configured: Stopped (fully_configured_stopped): Indicates that both the local system and the remote system have the partnership defined, and the partnership has been stopped on the local system.
Note: It is the partnership that is stopped, not the system.
Fully Configured: Remote Stopped (fully_configured_remote_stopped): Indicates that both the local system and the remote system have the partnership defined, and the partnership has been stopped on the remote system.
Note: It is the partnership that is stopped, not the system.
Fully Configured: Local Excluded (fully_configured_local_excluded): Indicates that both the local system and the remote system have the partnership defined; however, the local system is currently excluding the link to the remote system. This state usually occurs when the link between the two systems has been compromised by too many errors or slow response times of the partnership.
Fully Configured: Remote Excluded (fully_configured_remote_excluded): Indicates that both the local system and the remote system have the partnership defined; however, the remote system is currently excluding the link to the local system. This state usually occurs when the link between the two systems has been compromised by too many errors or slow response times of the partnership.
Fully Configured: Exceeded (fully_configured_exceeded): Indicates that both the local system and the remote system have the partnership defined; however, the partnership is disabled because the network of systems exceeds the number of systems allowed in partnerships. To resolve this error, reduce the number of systems that are partnered in this network. Partnerships can be defined between up to four systems in a network.

In addition to Fibre Channel and Fibre Channel over Ethernet (FCoE) connections, Metro Mirror and Global Mirror partnerships can be established over Ethernet links using the IPv4 and IPv6 addresses associated with Ethernet ports. These IP partnerships can be connections through Ethernet switches, or direct connections between local and partner systems. Partnerships must be created as either an IPv4 or IPv6 partnership. Data compression is also supported for IPv4 or IPv6 partnerships. To enable data compression, both systems in an IP partnership must be running a software level that supports IP partnership compression. To fully enable compression in an IP partnership, each system must enable compression. When compression is enabled on the local system, data sent to the remote system is compressed. To send compressed data to the local system, the remote system in the IP partnership must also enable compression.

Remote-copy groups are unique to IP partnerships and contain local and remote IP addresses accessible to each other through an IP partnership. A remote-copy group must contain at least one IP address in the local system and one IP address in the remote system. You must create the remote-copy groups before establishing the IP partnership.

Each Ethernet port can be associated with two IP addresses; one using IPv4 addressing and the other using IPv6. Use either IPv4 or IPv6 for IP partnership. You should configure more than two IP addresses within one system of the remote-copy group to allow for IP connection failover if the local or partner system experiences a node or port failure.

VLAN tagging of the IP addresses configured for IP partnerships is supported. IP partnerships create a remote-copy relationship between two volumes on two separate systems over an IP connection. For the systems in an IP partnership to access each other, the same VLAN ID must be configured for ports in the remote-copy group on both systems in an IP partnership. In addition, VLAN settings must be configured on the Ethernet network to prevent any connection issues.

To create a remote-copy partnership over an IP connection, complete these steps:

Configure VLAN tagging by completing these steps:
1. In the management GUI, select Settings > Network > Ethernet Ports.
2. Right-click the port on which to configure the VLAN and select Actions > Modify VLAN.
3. On the Modify VLAN page, select to enable VLAN for either IPv4 or IPv6 connections that are part of the remote-copy group.
4. Enter the VLAN tag and select whether to use the same VLAN tag for the failover port.
5. Click Modify.
Define the remote-copy groups on both the local and partner systems.
1. On the primary system, select Settings > Network > Ethernet Ports.
2. Right-click the port on which you configured the VLAN tag, and select Modify Remote Copy.
3. Depending on the type of IP connection you are using, select the remote-copy group to associate with the port.
4. Click Modify.
5. Repeat these steps on the remote system, ensuring that you use the same remote-copy group to ensure connectivity between the two systems.
Configure IP partnerships on the local system in the management GUI by completing these steps:
1. Select Copy Services > Partnerships and select Create Partnership.
2. On the Create Partnership panel, select IP.
3. Enter the following information to configure the partnership:
  Partner System IP Address
  
  Enter the IP address of the other system within the remote-copy partnership.
  
  Link Bandwidth
  
  Enter the amount of bandwidth that can be used for the IP connection between the systems within the partnership.
  
  Background Copy Rate
  
  Enter the maximum percentage of the link bandwidth that can be used for background copy operations.
  
  Partner System's CHAP Secret (Optional):
  
  Specify the CHAP secret for the partner system if you plan to use Challenge Handshake Authentication Protocol (CHAP) to authenticate connections between the systems in the partnership.
  
  Compression enabled
  
  Select this option if data on the local system is compressed before it is sent to the partner system. To fully enable compression in an IP partnership, each system must enable compression.
Configure IP partnership on the partner system in the management GUI by completing these steps:
1. Select Copy Services > Partnerships and select Create Partnership.
2. On the Create Partnership panel, select IP.
3. Enter the following information to configure the partnership:
  Partner System IP Address
  
  Enter the IP address of the other system within the remote-copy partnership.
  Note: This is the system that you configured in step 2.
  
  Link Bandwidth
  
  Enter the amount of bandwidth that can be used for the IP connection between the systems within the partnership. Use the same value that you specified in step 2.
  
  Background Copy Rate
  
  Enter the maximum percentage of the link bandwidth that can be used for background copy operations. Use the same value that you specified in step 2.
  
  Partner System's CHAP Secret (Optional):
  
  Specify the CHAP secret for the partner system if you plan to use Challenge Handshake Authentication Protocol (CHAP) to authenticate connections between the systems in the partnership. Use the same value that you specified in step 2.
  
  Compression
  
  Select this option if data on the local system is compressed before it is sent to the partner system. To fully enable compression in an IP partnership, each system must enable compression.

Using CHAP with an IP partnership (optional)

You can protect data exchange between the local system and partner system over an IP connection through challenge handshake authentication protocol (CHAP), which uses a shared secret to authenticate systems with each other when sending requests.

Note: You can also use a CHAP secret to authenticate with iSCSI-attached hosts. The system-wide CHAP secret is used for all CHAP authentication from the local system to partner systems and to iSCSI-attached hosts.

To configure CHAP for IP partnership, use the Modify CHAP Configuration dialog on each system to specify a system-wide CHAP secret, and select Use for IP partnerships. Two paths exist to this dialog in the management GUI:

Select Copy Services > Partnerships, then select Actions > Modify CHAP Configuration.
Select Settings > Network > iSCSI > Modify CHAP configuration.

Before creating an IP partnership, define a CHAP secret for each system, then configure CHAP to be used for IP partnerships on each system.

For example, when creating an IP partnership that uses CHAP between system A and system B, first define a CHAP secret on each system. The CHAP secret value on systems A and B can differ. On system A, specify the system B CHAP secret in the Create Partnership or Partnership Properties dialog, then on system B, specify the system A CHAP secret using one of the dialogs.

When creating an IP partnership on a local system using CHAP, if you do not specify the system-wide CHAP secret of the partner system, the local system displays a CHAP authentication failure message. If an IP partnership using CHAP is active, you must stop the partnership before modifying the CHAP configuration.