[j-nsp] CoS on iSCSI ports

Josh Farrelly Joshf at originit.co.nz
Tue Oct 14 18:39:51 EDT 2014

Hi all.

We have 2x EX4550's in VC that provide switching for an iSCSI network. There are 3 Dell SANs and 4 Dell R820 ESXi hosts connected via twinax @ 10Gbps. Jumbo frames and flow control is enabled.

My knowledge around Juniper tech is a little vague, but what's with the default CoS settings on the switch? It seems they will automatically reserve 5% for network control traffic. Is there anyway to disable CoS entirely? AFAIK Brocade & Cisco don't have this type of default, and 5% of a 10Gbps is actually a rather significant chunk of bandwidth.

The reason I'm asking is that we've seen some performance issues lately. We have a hybrid-SSD tray of storage that can saturate a link, so we're seeing MAC pause frames being received by the switch as well as discards on some of the queues.

Thanks for any pointers.



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