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O/S Deployment Thread, Server 2012 WDS Multicasting slowwwww in Technical; Have managed to get my 2012 server up and running with MDT using WDS for PXE booting clients. Works a ...
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    fiza's Avatar
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    Server 2012 WDS Multicasting slowwwww

    Have managed to get my 2012 server up and running with MDT using WDS for PXE booting clients. Works a charm on my 2 test machines using Unicast but when I enable Multicast and try it then the deployment goes from 25 minutes for both machines to over 2 hours for same image same machines.

    Server and clients are all connected to core switch (which has IGMP enabled). I havent enabled IGMP on any of my other switches yet.

    I have googled and the only info I can find is about reducing the APBlockSize. In WDS for Server 2012 it is already set low by default.

    When Multicasting the Transfer rate jumps around from 54KBps to 4000KBps.

    I have split the WDS setting so that clients are split into 3 sessions (slow, medium & fast) but both clients jump transfer rates at the same level.

    I am getting closer to the point where I need to start imaging whole IT Suites so I need to get Multicasting sorted.

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    Same issue here, many google searches state the same; that unicast is far faster than multicast (up to a certain amount of computers being deployed).

    For now, we just cancel the multicast and deploy via unicast...

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    Quote Originally Posted by MYK-IT View Post
    Same issue here, many google searches state the same; that unicast is far faster than multicast (up to a certain amount of computers being deployed).

    For now, we just cancel the multicast and deploy via unicast...
    How big is your image? How long does the imaging take with Unicast?
    How many have you tried with unicast in one go?

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    Have you any unmanged switches/hubs floating around on your network anywhere?

    When I was multicasting in the summer I disconnected parts of the network with any unmanaged networking device on (not my doing, still trying to replace with managed stuff) and it boosted the speed no end. There was one client in one room for some reason that slowed the multicast for whatever reason, just disconnected that one and did it seperately from the rest.

    Might be worth disconnecting parts of your network from the core to see if you can narrow down any particular area that's causing a problem during a multicast?

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    fiza's Avatar
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    Quote Originally Posted by Cache View Post
    Have you any unmanged switches/hubs floating around on your network anywhere?

    When I was multicasting in the summer I disconnected parts of the network with any unmanaged networking device on (not my doing, still trying to replace with managed stuff) and it boosted the speed no end. There was one client in one room for some reason that slowed the multicast for whatever reason, just disconnected that one and did it seperately from the rest.

    Might be worth disconnecting parts of your network from the core to see if you can narrow down any particular area that's causing a problem during a multicast?
    There are a couple in other buildings but if the clients and WDS server all connected to same igmp enabled switch surely the switches in the other areas shouldnt affect it?

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    Quote Originally Posted by fiza View Post
    There are a couple in other buildings but if the clients and WDS server all connected to same igmp enabled switch surely the switches in the other areas shouldnt affect it?
    I thought this, but it just about brought the network to it's knees when doing multicasting. Maybe I don't have it configured right, but the unmanaged stuff was throwing all the multicast traffic back into the network as broadcast unicast (I think), so would be worth checking out.

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    there is a patch from MS to resolve this issue. A friend had exactly same same issue and eventually found a hotfix.

    I will try to get the kb

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    Quote Originally Posted by deano View Post
    there is a patch from MS to resolve this issue. A friend had exactly same same issue and eventually found a hotfix.

    I will try to get the kb
    This is the KB Dean was referring to: Multicast Deployment Fails from Windows Deployment Services (WDS) - worth a look.

    Also, just out of curiosity, you don't happen to have Hyper-V installed with a virtual switch configured for the VM's do you?

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    Quote Originally Posted by mattjones View Post
    This is the KB Dean was referring to: Multicast Deployment Fails from Windows Deployment Services (WDS) - worth a look.


    Also, just out of curiosity, you don't happen to have Hyper-V installed with a virtual switch configured for the VM's do you?
    This is what I was referring to in my original post about the APBlock size. On 2012 its already set low.

    I do have Hyper-V with a virtual switch set up but not on the WDS server.

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    MDT isn't in a VM or on the same server as Hyper-V is it?

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    Does this mean that MDT2012 running as a Hyper-V VM cannot support Multicast using a Virtual Switch?

    If so, would that explain why we always use Unicast as Multicast takes many. many times longer?

    Thanks

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    Quote Originally Posted by mattjones View Post
    MDT isn't in a VM or on the same server as Hyper-V is it?
    No. MDT/WDS on a physical server.

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    We noticed an issue that when Hyper-V was using the same NIC via a virtual switch that the MDT server was using for deployment, the speeds were very slow. It could be a possibility MYK-IT - based on our experience.

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    HI there,

    We're having similar issues, our server (server 2012 with MDT 2013) is a VM running on vmware 5.0 and the multicast is very slow. Is multicast not recommended on servers that are VM?

    Thanks,

    Ash.

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    I found it was very reliant on the virtual nic. I think ESX has a few you can try. We use hyper v here and we had to change this registry entry
    [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\WDSServer\Providers\WDSMC\Protocol]

    "TpMaxBandwidth"=dword:00000001

    Its set too 100 (decimal) by default. Which is fine if your clients have the same nic speed as the server. After dropping it to 1 we had less errors as the wds/mdt server was sending packets to the network at 100mbps rather than 10gbps. In testing using esx I had to change to use a emulation nic. The thing with multicast is that it needs to work with your slowest client usually 100mbps.

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