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Replication over a Slow Link - Lots of Traffic

    Question

  • I have a problem that I just can't get to the bottom of..

    We replicate a customers VM back to our office.

    At our end (remote end) with have a Server 2012 R2 Hypervisor and at his end (Primary end) we have a Server 2012 Hypervisor.

    The connection is slow..., not dire..., but slow..

    I have just built a new server at his office that is replicating back to us... There is nothing on this server yet.., so no AV, no SQL, shadow copy is turned off.., nothing on it..., just a virgin server..

    As a test on my new VM, I run a Windows Update and select 100mb of updates and apply them.. They install, and all is fine..

    Replication kicks in, and I can see that 2.3gb! is replicating back to us... This seems to happen every time anything happens on the server.., we always get this massive amount of data being replicated back to us, and this of course then starts backing up and we end up with problems...

    I'm guessing that this is a well known problem, but I could really do with some advice on ways around it...

    Thanks in advance..

    Saturday, April 22, 2017 8:57 AM

Answers

  • Okay, I think we have an answer here!

    It is down to the VM's being dynamically expanding..., if I make them fixed size it behaves normally..., or as good as it's going to get over a slow link..

    You don't get this with Server 2012R2..., it seems to just be Server 2012..

    • Marked as answer by CPA-UK Wednesday, May 17, 2017 3:42 AM
    Wednesday, May 17, 2017 3:42 AM

All replies

  • Anybody have any ideas about this one...?

    I don't think it is swap files and as there is nothing running on this newly built server yet, nothing is changing..., or so it appears...

    Every change to the server at the customers site kicks off a replication of around 2GB back to our DR site...


    • Edited by CPA-UK Monday, April 24, 2017 3:05 PM
    Monday, April 24, 2017 2:59 PM
  • Hi Sir,

    Generally , the network traffic depends on the hrl (hyper-v replica log) file which located in primary server after the change was made on that vhd .

    Regarding hyper-v replica please check this blog:

    http://www.altaro.com/hyper-v/how-hyper-v-replica-actually-works/

     

    I also tested in my lab , I only copied a file to primary VM , the size of .hrl file almost equal to the file I copied .

     

    In your case , the update might be different than file copy , because , we don't know the exact changes which was made by that update (the update file might be compressed ).

    In addition , the network traffic should be compressed by 'network module' of hyper-v replica while you checked the option 'Compress the data that is transmitted over the network' :

     


    Best Regards,

    Elton


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    Tuesday, April 25, 2017 9:02 AM
    Moderator
  • Thanks for your thoughts on this one, but it didn't resolve the problem..

    On the 2nd VM we have now moved the swapfile over to a separate vhdx file which is not replicated and the problem still exists...

    Compression is enabled on the replication...

    We are wondering if this is unique to Server 2012 as we have never had this issue with any of our 10+ Server 2012R2 servers...?

    Could it also be that the link is slow..?, ADSL, 10mb Down and 0.5 Up...

    Any other takers on this one..?

    Thursday, May 11, 2017 4:24 AM
  • Okay, I think we have an answer here!

    It is down to the VM's being dynamically expanding..., if I make them fixed size it behaves normally..., or as good as it's going to get over a slow link..

    You don't get this with Server 2012R2..., it seems to just be Server 2012..

    • Marked as answer by CPA-UK Wednesday, May 17, 2017 3:42 AM
    Wednesday, May 17, 2017 3:42 AM