UNSOLVED Multicast sometimes fast sometimes extremely slow

  • Hey guys I’m multicasting and some time I get 7-10 gbs per minute taking around 10-20 minutes to do 30 PCs. Some times for the same 30 I get 2-3 gbs per minute. Taking around 30-40 minutes now I’m getting 100-200 mbs per minute taking over 6 hrs. What gives? They all have 1 GIG uplink

  • Moderator

    Just in the fwiw bucket, we recently found out that if you have 2 or more simultaneous multicasts streams going at one time, the trasfer rates drop off quite a bit. I do remember seeing someone create a patch to change the multicast base IP address with each new stream. That seemed to resolve the issue.

    [edit] Updated info: https://forums.fogproject.org/topic/12300/multicast-data-address-not-change-from-one-task-to-another-one/16

  • Senior Developer

    @tesparza Please let us know your findings to see if those instructions might help others troubleshooting as well. Would be interesting to see what is causing it for you in the end.

  • @Sebastian-Roth Okay will troubleshoot, I did not know that one slow PC slowed down everyone. Thanks I will look into grouping to see which one is slowing it down.

  • Senior Developer

    @tesparza said in Multicast sometimes fast sometimes extremely slow:

    They all have 1 GIG uplink

    Are you absolutely sure? It needs just one slow PC out of 30 in a multicast session to cause the whole lot to be very slow. Have you checked all link speed LEDs on the clients?

    Possibly on one of the clients a hard disk is going to die soon and is making the whole machine and therefor the multicast session slow.

    It’s impossible for us to diagnose this as we don’t have access to your (network) setup and debug this. You need to do tests to find if some of the machines are making more issues than others. Split the group of 30 into batches of 5 PCs and multicast to those. Try every batch at least three times in a row and note down all the speeds and times. When you find one 5er batch to be slow take out lets say number one and test on 2, 3, 4 and 5. Again slow? Then multicast to 1, 3, 4 and 5. This way you should be able to figure out which PC(s) exactly are causing the slowness.