[dm-devel] Multipath not using multiple NICs at once

[Eric]

Hello,

I'm fairly new to multipath and I am having an issue with it not using 
all of my NICs. Currently, my node has 4 gigE NICs to my storage network 
and the SAN has 8 gigE NICs to the same network and I am attempting to 
setup multipath with ISCSI in order to utilize more than 1 gigabit 
connection. However, when I use nload to check the network usage, you 
can see the traffic hop around the NICs. For example, data would send 
for 2-3 seconds on eth1, then stops and starts on eth2, then stops and 
starts back up on eth3. All perfectly distributed, but in this setup, 
unable to reach beyond the capacity of a 1 gigabit connection.

I have each NIC on a different network (e.g. 10.1.1.0/24 for eth1, 
10.1.2.0/24 for eth2, etc.). Netstat shows that the connections are 
being made each to different IPs:

tcp        0      0 10.1.3.8:35493          10.1.5.241:3260 ESTABLISHED
tcp        0      0 10.1.3.8:53972          10.1.3.241:3260 ESTABLISHED
tcp        0      0 10.1.6.8:41090          10.1.4.241:3260 ESTABLISHED
tcp        0      0 10.1.1.8:50754          10.1.1.241:3260 ESTABLISHED
tcp        0      0 10.1.6.8:49780          10.1.5.241:3260 ESTABLISHED
tcp        0      0 10.1.1.8:36938          10.1.6.241:3260 ESTABLISHED
tcp        0      0 10.1.6.8:52009          10.1.6.241:3260 ESTABLISHED
tcp        0      0 10.1.5.8:51630          10.1.1.241:3260 ESTABLISHED
tcp        0      0 10.1.5.8:54481          10.1.4.241:3260 ESTABLISHED
tcp        0      0 10.1.1.8:54504          10.1.5.241:3260 ESTABLISHED
tcp        0      0 10.1.5.8:58229          10.1.3.241:3260 ESTABLISHED
tcp        0      0 10.1.3.8:49031          10.1.1.241:3260 ESTABLISHED
tcp        0      0 10.1.5.8:40551          10.1.6.241:3260 ESTABLISHED
tcp        0      0 10.1.4.8:45016          10.1.5.241:3260 ESTABLISHED
tcp        0      0 10.1.4.8:55665          10.1.4.241:3260 ESTABLISHED
tcp        0      0 10.1.6.8:57472          10.1.3.241:3260 ESTABLISHED
tcp        0      0 10.1.6.8:39278          10.1.1.241:3260 ESTABLISHED
tcp        0      0 10.1.4.8:41329          10.1.6.241:3260 ESTABLISHED
tcp        0      0 10.1.5.8:33553          10.1.5.241:3260 ESTABLISHED
tcp        0      0 10.1.3.8:48950          10.1.6.241:3260 ESTABLISHED
tcp        0      0 10.1.4.8:54752          10.1.1.241:3260 ESTABLISHED
tcp        0      0 10.1.1.8:40911          10.1.4.241:3260 ESTABLISHED
tcp        0      0 10.1.4.8:41135          10.1.3.241:3260 ESTABLISHED
tcp        0      0 10.1.3.8:44606          10.1.4.241:3260 ESTABLISHED
tcp        0      0 10.1.1.8:54677          10.1.3.241:3260 ESTABLISHED

(10.1.*.8 is the node and 10.1.*.241 is the SAN)

Here is my /etc/multipath.conf:

defaults {
         path_grouping_policy    multibus
         path_selector           readsector0
         polling_interval        3
         path_selector           "round-robin 0"
         failback                immediate
         features                "0"
         no_path_retry           1
         rr_weight               uniform
         rr_min_io               100
#       user_friendly_names     yes
}

Both servers are running Ubuntu 12.04LTS.

Any ideas?

Thanks,
Eric