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Distributed Cache and SharePoint 2016 - 3 servers still the max?

    Question

  • I am in the middle of architecting a new SharePoint 2016 farm and want to clarify any restrictions regarding number of servers running the distributed cache. In 2013 we found out via an error in CA and then researching said error that if you are running 4 or more servers you are not supposed to run the distributed cache on all of the servers (thus a max of 3 servers).  Is this still true in SharePoint 2016?  The error page has been updated for 2016 which leads me to believe this is true (https://technet.microsoft.com/en-us/library/jj891124(v=office.16).aspx ) but just like 2013 this limitation is not listed on any architecture diagrams that I have found (you would think a limitation like this would actually be documented somewhere Microsoft...).  Thanks!
    Wednesday, March 15, 2017 5:34 PM

Answers

  • Limits are outlined here:

    https://technet.microsoft.com/en-us/library/cc262787(v=office.16).aspx#Velocity

    TL;DR: 16

    That said, unless you have a multi-hundred thousand user deployment with small memory allocation to DC, such a large DC deployment wouldn't be necessary.


    Trevor Seward

    Office Servers and Services MVP



    Author, Deploying SharePoint 2016

    This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.

    Wednesday, March 15, 2017 6:32 PM
    Moderator

All replies

  • Limits are outlined here:

    https://technet.microsoft.com/en-us/library/cc262787(v=office.16).aspx#Velocity

    TL;DR: 16

    That said, unless you have a multi-hundred thousand user deployment with small memory allocation to DC, such a large DC deployment wouldn't be necessary.


    Trevor Seward

    Office Servers and Services MVP



    Author, Deploying SharePoint 2016

    This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.

    Wednesday, March 15, 2017 6:32 PM
    Moderator
  • Hi Trevor,

    Thanks for the response!  I apologize; I should have phrased my question as max without potentially experiencing reliability and performance problem (I had already seen the 16 hosts which is the same from the 2013 documentation). 

    What is funny is that while they state 16, if you have it on more than 3 servers in a farm they have a health analyzer rule set to throw a severity 1 error:

    "The number of Distributed Cache hosts in the farm exceeds the recommended value"

    "On a farm with four or more servers, you must not start the Distributed Cache service on all servers on the farm. You can only run Distributed cache on servers that are configured as  Distributed cache role in SharePoint Server 2016 MInRole. If you configure all servers as cache hosts, you may experience reliability and performance problems in the farm."

    So on one hand they say you can have up to 16 and then on the other if you have more than 3 in a farm you may experience reliability and performance problems.  Nowhere that I can find is this documented other than the error references (for redundancy in our 2013 farm we had the DC running on 4 servers until we started getting this error).  Am I missing something?

    Tim

    Wednesday, March 15, 2017 7:46 PM
  • I read it this way, If you have farm with four or more server then you should not start the DC on All servers in the farm. that's being said if you start the DC on all servers with 4+ server farm then you will see issues...if you have 10 server farm and started the DC on 6 servers u will be fine.

    I have a farm with 15+ servers and DC running on 6 servers but never seen this health alert.


    Please remember to mark your question as answered &Vote helpful,if this solves/helps your problem. ****************************************************************************************** Thanks -Waqas Sarwar(MVP) Blog: http://krossfarm.com

    Wednesday, March 15, 2017 7:55 PM
    Moderator
  • Thanks Waqas!  It is one of those cases where my setup narrowed my focus.  So the limit in reality is the lesser of 16 or 1 less than the total number of servers (if above 4 servers in the farm). 
    Wednesday, March 15, 2017 8:02 PM
  • Yes, less than the total number of server with maximum of 16. But i dont think anybody really need 16 unless a 365 type dpeloyment :)

    Please remember to mark your question as answered &Vote helpful,if this solves/helps your problem. ****************************************************************************************** Thanks -Waqas Sarwar(MVP) Blog: http://krossfarm.com

    Wednesday, March 15, 2017 8:15 PM
    Moderator