Using SnapMirror over multiple paths

Two modes of multiple paths

You might need more than one physical path for a mirror. SnapMirror supports up to two paths for a particular SnapMirror relationship. The paths can be Ethernet, Fibre Channel, or a combination of Ethernet and Fibre Channel. The two paths can be used in one of two modes:

Multiplexing mode--SnapMirror uses both paths at the same time, essentially load balancing the transfers. If one path fails, the transfers occur on the remaining path. After the failed path is repaired, the transfers resume using both paths.
Failover mode--SnapMirror uses the first specified path as the desired path and use the second specified path only after the first path fails.

Setting up SnapMirror using multiple paths

To implement multiple paths between the source and destination storage system, complete the following steps.

Step	Action
1	Ensure that you have two valid paths using the `ping` command from the source system to each of the IP addresses on the destination system. Example The IP addresses on the destination system are 10.10.10.23 and 10.10.10.24. source> `ping 10.10.10.24` 10.10.10.24 is alive source> `ping 10.10.10.23` 10.10.10.23 is alive
2	If you are...	Then...
	Setting up SnapMirror for the first time and want to use multiple paths	Follow the steps shown in Setting up a basic SnapMirror operation, then follow Step 3 and Step 4.
	Converting a single path SnapMirror	Follow Step 3 and Step 4.
3	On the administration host, edit the snapmirror.conf file on the destination system to add a connection name line that defines the mode of the connection and what the two connections are. The format of the line follows: name = mode (src_system1, dest_system1) (src_system2, dest_system2) mode is either multi or failover. See the na_snapmirror.conf(5) man page for details.
4	In the same snapmirror.conf file, edit the schedule entry to reflect the new connection name as the source system.

Note
Multiple paths are supported by SnapMirror running asynchronously and synchronously. The following are examples of implementing multiple paths using synchronous SnapMirror.

Example 1

You want to synchronously mirror volume vol1 on a storage system called NYC to volume vol1 on a storage system called Newark. To satisfy a business requirement that there be two paths between each synchronously mirrored volume, you have four network interface cards, two in each system. You named the two interfaces on the NYC system NYC-pri and NYC-sec and the two on the Newark system Newark-pri and Newark-sec. To implement multiple paths in failover mode, you edit the snapmirror.conf file on Newark to include the following two lines:

NYC-Newark = failover (NYC-pri, Newark-pri) (NYC-sec, Newark-sec)

NYC-Newark:vol1 Newark:vol1 - sync

Example 2

If NYC-pri and Newark-pri are Fibre Channel adapters and you want to replicate data using both connections, you follow the procedure to configure Fibre Channel adapters for SnapMirror. See Configuring for Fibre Channel use. Then you edit the snapmirror.conf file on Newark to include the following two lines to implement multiple paths in multiplexing mode:

NYC-Newark = multi (NYC-pri, Newark-pri) (NYC-sec, Newark-sec)

NYC-Newark:vol1 Newark:vol1 - sync