[j-nsp] CoS on iSCSI ports

[Mike Gonnason]

For my iSCSI stuff, I have been disabling pause frames as they are not
really beneficial for my situation. I had a NetApp (forget what model) that
would saturate a 10Gb link and the Juniper would send a pause frame with
the result of dropping all connections across that trunk. Not very helpful.

You can try modifying the NC class and alter how the scheduling is
performed. in section 21 you can see 5% is specified for the NC scheduler.

http://www.juniper.net/documentation/en_US/junos13.2/topics/example/cos-ex-series-configuring.html


-Mike Gonnason

On Tue, Oct 14, 2014 at 3:39 PM, Josh Farrelly <Joshf at originit.co.nz> wrote:

> 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.
>
> Regards,
>
> Josh.
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