z/VM Virtual Switch Link Aggregation
Link Aggregation (LAG) support for the virtual switch was first introduced in z/VM starting with z/VM Release 5.3. The virtual switch configured in Ethernet mode supports the aggregation of multiple OSA-Express features for external LAN connectivity. By supporting IEEE 802.3ad Link Aggregation, the combination of multiple OSA-Express features appears as one large link. The deployment of this type of configuration increases the virtual switch bandwidth and provides near seamless failover in the event that a port becomes unavailable.
This support provides the ability to aggregate physical OSA-Express features for use by a single virtual switch (Exclusive mode) or to shared by multiple virtual switches (Multi-VSwitch LAG) mode.
Both Exclusive and Multi-VSwitch LAG configurations provide the same industry standard IEEE 802.3ad Link Aggregation protocol support with an external partner switch. Both of these LAG configurations are completely transparent to z/VM guest hosted by either a simulated NIC connected directly to the VSwitch or a HiperSockets Bridge NIC connection.
The primary difference between these two configurations is the LAG sharing characteristics. A LAG (Link Aggregation Group) is exclusively used by a single virtual switch or shared by multiple virtual switches. Some comparisons between the two LAG deployments:
|Comparison Item||Exclusive LAG||Multi-VSwitch LAG|
|Application||Simpler for a single system LAG.||Multiple VSwitch access to the same network.|
|OSA-Express Resources||Dedicated networking ports service one VSwitch. Volume of network traffic requires high bandwith and throughput.||Shared resources result in a reduction of physical ports that are more fully utilized.|
|Network Access||Network access is limited to a single z/VM system and VSwitch.||Access to the network can span multiple VSwitches within a z/VM system and across many z/VM systems within the CEC.|
|Port Group Management||Must be managed (configuration) on the z/VM system that the port group was defined.||Can be managed on any z/VM system within the same IVL domain.|
|Physical Switch Partner||Each exclusive LAG requires a separate and distinct physical LAG to be configured and managed on the partner switch.||Only a single LAG configuration required to support a Multi-VSwitch LAG configuration. The single physical LAG provides network connectivity and high availability for all z/VM systems within the same CEC.|
|z/VM Support||z/VM 5.3 or higher.||z/VM 6.3 with APARS VM65583 and PI21053.|
|Hardware Support||z9 EC and z9 BC processors or higher and OSA-Express2 or higher.||OSA-Express4S & OSA-Express5s support for Multi-VSwitch Link Aggregation requires an IBM z13 with Driver 22H with a minimum Bundle level of S11a with MCL N98805.007.|
For more information about Link Aggregation with the z/VM Virtual Switch, see:
- "Virtual Switch Link Aggregation" in the Connectivity book in the Library
- "z/VM 6.3 Virtual Switch Enhancements for the z13" (June 2015)
- "z/VM Multi-VSwitch LAG Configuration and Operational Demonstration 101" (June 2015)
- "VM Highly Available Network Whitepaper" (December 2009)
Hints and Tips
Here are some examples of configuration errors that may occur and how to detect and correct them:
- Exclusive use errors
- Unsupported OSA-Express features
- Mixing Different levels of OSA-Express features
Here are some Multi-VSwitch LAG best practices:
- It is recommended that the IVL network bandwith match the bandwidth of the links within the LAG port group. For example, if the port group is composed of 10G OSA-Express features, then the IVL should also be deployed with 10g OSA-Express features. This will insure that the IVL network will have enough bandwith to support potential failover situations.
- For configurations that deploy one or two VSwitches per z/VM system, the two controllers provided by z/VM will be sufficient. Even though a given controller can service more than one VSwitch, optimum operational performance is achieved when there is a one to one pairing of VSwitch to controller. For more information see z/VM Connectivity chapter "Virtual Switch Controller Configuration Strategy" in the Library.
Please direct questions, comments and feedback regarding z/VM's Link Aggregation support or any of the information on this page to either:
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