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vSAN Multicast performance test fails (2135495)

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Symptoms

  • The vSAN (formerly known as Virtual SAN) Multicast performance test fails showing a received bandwidth of 0.00 MB/s. This can be seen by running this RVC command at the cluster level:

    vsan.health.multicast_speed_test 0

  • Running the Proactive test on the Web client also shows it as Failed for certain hosts in the cluster. The list of hosts will not include the host from which  the test is initiated.
  • Running the tcpdump command shows each host receiving multicast traffic from each host in the cluster.


Purpose

To work around the failure of vSAN Multicast performance test, create a private network on 2 ESXi hosts in the cluster, set a mulitcast group address in that network, and then monitor the results using iperf.

Resolution

This is a known issue affecting the vSAN Health plugin for vSAN 6.1/6.2.

Note: In this example the vmk2 interface is set up on a private network 192.168.0.*

Caution
: This test should not be run in a production environment. This should be tested before any production virtual machine is added to the vSAN cluster. 

To work around the issue and test the multicast performance, you need to create a private network on 2 ESXi hosts in the cluster, set a mulitcast group address in that network, and then monitor the results using iperf.

To run the test:
  1. Manually create a private network on two  hosts and set the static IPs as 192.168.0.1 and 192.168.0.2.
  2. On each host, run this command to check the current routing table:

    esxcli network ip route ipv4 list

    At this point the routing table looks similar to:

    default      0.0.0.0        10.160.63.253  vmk0       DHCP
    10.160.32.0  255.255.224.0  0.0.0.0        vmk0       MANUAL
    192.168.0.0  255.255.255.0  0.0.0.0        vmk2       MANUAL


  3. Create a temporary multicast group within the private network to test performance. On each host, bind the multicast group address to this network using this command: 

    esxcli network ip route ipv4 add -n 224.2.3.4/32 -g 192.168.0.0

    Where 192.168.0.0 is the vSAN Network and 224.2.3.4 is the default multicast network used for vSAN.


    Check the routing table again, it should look similar to:

    default      0.0.0.0          10.160.63.253  vmk0       DHCP
    10.160.32.0  255.255.224.0    0.0.0.0        vmk0       MANUAL
    192.168.0.0  255.255.255.0    0.0.0.0        vmk2       MANUAL
    224.2.3.4    255.255.255.255  192.168.0.0    vmk2       MANUAL



  4. Run iperf server and client to test that the new multicast group is working:

    On server side (192.168.0.2)

    [root@sc-rdops-vm02-dhcp-38-134:/usr/lib/vmware/vsan/bin] ./iperf.copy -y C -s -B 224.2.3.4 -u -i 1

    Note: The iperf.copy file is not present in a newly provisioned ESXi host, it is created by the vSAN health plug-in at first start up.

    On client side (192.168.0.1)

    [root@sc-rdops-vm02-dhcp-58-79:/usr/lib/vmware/vsan/bin] ./iperf -y C -c 224.2.3.4 -u -w 1M -b 1M -t 10 -i 5
    20150709093103,192.168.0.1,45564,224.2.3.4,5001,3,0.0-5.0,626220,1001952
    20150709093108,192.168.0.1,45564,224.2.3.4,5001,3,5.0-10.0,624750,999600
    20150709093108,192.168.0.1,45564,224.2.3.4,5001,3,0.0-10.0,1252440,999896


  5. Run the multicast performance test from the vSAN Health, monitor and note the results.
  6. Remove the temporary  multicast group route using this command:

    esxcli network ip route ipv4 remove -n 224.2.3.4/32 -g 192.168.0.0

Additional Information

This issue is mentioned in the VMware Virtual SAN 6.1 Release Notes.
 
For more details on the multicast performance test, see section 7.2 in the Virtual SAN Health Check Plug-in Guide.
 

Tags

vSAN Multicast performance test

See Also

Update History

02/03/2017 - Added vSAN 6.5 to Products.

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