[lustre-discuss] weird issue w. lnet routers

john casu john at chiraldynamics.com
Tue Nov 28 19:40:08 PST 2017

just about to try that MTU setting.

It's a small lustre system... 2 routers, MDS/MGS pair, OSS pair, JBOD pair (112 drives for OST)
and yes, routing between EDR & 100GbE


On 11/28/17 7:28 PM, Raj wrote:
> John, increasing MTU size on Ethernet side should increase the b/w. I also have a feeling that some lnet routers and/or
> intermediate switches/routers does not have jumbo frame turned on (some switches needs to be set at 9212 bytes ).
> How many LNet  routers are you using? I believe you are routing between EDR IB and 100GbE.
> On Tue, Nov 28, 2017 at 7:21 PM John Casu <john at chiraldynamics.com <mailto:john at chiraldynamics.com>> wrote:
>     just built a system w. lnet routers that bridge Infiniband & 100GbE, using Centos built in Infiniband support
>     servers are Infiniband, clients are 100GbE (connectx-4 cards)
>     my direct write performance from clients over Infiniband is around 15GB/s
>     When I introduced the lnet routers, performance dropped to 10GB/s
>     Thought the problem was an MTU of 1500, but when I changed the MTUs to 9000
>     performance dropped to 3GB/s.
>     When I tuned according to John Fragella's LUG slides, things went even slower (1.5GB/s write)
>     does anyone have any ideas on what I'm doing wrong??
>     thanks,
>     -john c.
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