Hi Robert,

> Another option is if both RDMA ports are on the same card, then you can do 
> RDMA with a bond. This does not work if you have two separate cards.

Yes, we recently talked to Mellanox and their engineers also recommend this way.

> As far as your questions go, my guess would be that you would want to have 
> the different NICs in different broadcast domains

yes, the idea was to use two public networks on two different NICs with 
addresses from different subnets. It is possible to set 2+ networks in Ceph 
configuration, but it’s unclear how Ceph is going to use this configuration.

> or set up Source Based Routing and bind the source port on the connection 
> (not the easiest, but allows you to have multiple NICs in the same broadcast 
> domain). I don't have experience with Ceph in this type of configuration.

it’s too complicated and, frankly, when you’re trying to reach max performance, 
Source Based Routing is a bit from another area :-)

At the end of the all, we’re going to test bonding of two ports on same NIC.

Thank you.

-- 
Volodymyr Litovka
  "Vision without Execution is Hallucination." -- Thomas Edison

> On Fri, Aug 2, 2019 at 9:41 AM Volodymyr Litovka <[email protected] 
> <mailto:[email protected]>> wrote:
> Dear colleagues,
> 
> at the moment, we use Ceph in routed environment (OSPF, ECMP) and everything 
> is ok, reliability is high and there is nothing to complain about. But for 
> hardware reasons (to be more precise - RDMA offload), we are faced with the 
> need to operate Ceph directly on physical interfaces.
> 
> According to documentation, "We generally recommend that dual-NIC systems 
> either be configured with two IPs on the same network, or bonded."
> 
> Q1: Did anybody test and can explain, how Ceph will behave in first scenario 
> (two IPs on the same network)? I think this configuration require just one 
> statement in 'public network' (where both interfaces reside)? How it will 
> distribute traffic between links, how it will detect link failures and how it 
> will switchover?
> 
> Q2: Did anybody test a bit another scenario - both NICs have addresses in 
> different networks and Ceph configuration contain two 'public networks'? 
> Questions are same - how Ceph distributes traffic between links and how it 
> recovers from link failures?
> 
> Thank you.
> 
> --
> Volodymyr Litovka
>   "Vision without Execution is Hallucination." -- Thomas Edison
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