On Tuesday, 11/20/2007 at 01:02 EST, Pieter Harder <[EMAIL PROTECTED]> wrote: > To be more precise: I am looking for some guidelines what to expect for a > single Vnic talking to multiple targets. Alan pointed to the z/VM performance > documents for general LA performance, but that does not address what I am > asking for. > > Theoretical: when I aggregate 8 10GbE OSA's I have a throughput of 8 GB/s. Can > I expect a single Vnic to handle that traffic? Obviously not. But what can I > expect? What does it depend on?
Not "obviously not". :-) The first time a VNIC talks to a particular destination MAC, an OSA is selected and bound. All subsequent communication by that same VNIC with that same MAC will use the same OSA. If the OSAs become sufficiently unbalanaced, then a new OSA is selected and the VNIC traffic to that same MAC is moved. (Read the discussion in the z/VM Connectivity book about load balancing.) Consequently, communications between a single VNIC and a single MAC will not consume more than one OSA's worth of bandwidth. This means that if 100% of your traffic to a guest is via a router (all destination MACs belong to the router), you may want to define multiple default gateways so that the non-local traffic is sprayed to multiple MACs, letting the VNIC throughput exceed a single OSA. While the algorithm may seem limited, it was designed to more efficiently handle many VNICs sharing the port group rather than a single VNIC consuming all the bandwidth. Depending on what kind of results people see in their shops, we might consider looking at a more sophisticated algorithm for OSA selection. E.g. We could change the algorithm to use IP addresses instead of MACs. Alan Altmark z/VM Development IBM Endicott ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
