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If your message was personal or of a "non-urgent" nature, I'll reply as soon as I can. Wayne >>> Andrew Hines <[email protected]> 11/25/13 05:29 >>> Hello, This will not help to answer James´s question, but I want to take the opportunity to relate a very interesting experience we had with our core LAGs just last week. What I am about to relate may be common knowledge to everyone but myself, in which case please forgive the waste of your time. Our two data center switches are connected to our backbone switch via LAGs with 3 physical gigabit links. Peak utilization has historically been about 1.5 gigabits. Then last week the systems guys decided to start syncing some of their SAN disks via the ethernet network instead of their fiber channel network ("hey man we have another 1.5 gigs to spare"). This synchronization began consuming 1 gig of bandwidth, but because it was a single flow between two IP addresses the entire gig of traffic was assigned to a single physical gig link. Has anyone ever stopped to ponder such a situation? Does the switch act like a load balancer and move the existing traffic or new flows to one of the other lesser used links? Well the answer appears to be no. And just let me warn you that the havoc created is not so easy to diagnose becuase it is not just a simple binary connectivity issue. Some things work fine, others that just happen to have the LAG hash algorithm choose the oversubscribed link don´t work. The only true way to discern what was happening was analyzing the individual link graphics where we saw that one of the individual links was oversubscribed causing massive packet discards (I have attached a photo but not sure if it will make it through to the list). So the moral of the story is to monitor utilization on both the LAG and all the individual links that make up the LAG... -Andrew --- To unsubscribe from enterasys, send email to [email protected] with the body: unsubscribe enterasys [email protected] --- To unsubscribe from enterasys, send email to [email protected] with the body: unsubscribe enterasys [email protected]
