There is a guidance from Microsoft to be followed with virtual machines (VM) running SharePoint 2013. The guidance is “you must not configure the VM with Dynamic Memory”.
There are two issues if you do configure the VM with dynamic memory:
- Not supported by Microsoft SharePoint Product team
In fact, the Dynamic Memory setting is referenced in a Microsoft article on unsupported scenarios “Certain Microsoft SharePoint Server 2013 installation scenarios are not supported”
This article describes Microsoft SharePoint Server 2013 installation scenarios that are not supported:
You install SharePoint Server 2013 on a virtual machine (VM) that uses Dynamic Memory. For more information about best practice configurations for SharePoint Server 2013 and virtual machines, go to the following Microsoft TechNet website: Use best practice configurations for the SharePoint 2013 virtual machines and Hyper-V environment
The Distributed Cache service can run on either a physical or virtual server. When using virtualization, do not use Dynamic Memory to manage shared memory resources among other virtual machines and the Distributed Cache servers. The memory allocation for virtualized Distributed Cache servers must be fixed. Source: http://technet.microsoft.com/en-us/library/jj219572(v=office.15)
The memory allocation for virtualized Distributed Cache servers must be fixed.
OK, so that’s Microsoft world – so Microsoft Hyper-V. What about VMware then?
Until now, I haven’t found any guidance on for Vmware as all the official documentation mentions “Dynamic Memory” which alludes to the setting in Microsoft Hyper-V.
It is important that the cache cluster runs in a homogeneous environment of servers. It is not supported for cache hosts to have different physical specifications in memory, processor speed, and other capabilities.
The cache cluster is a collection of one or more instances of the Caching Service working together in the form of a ring to store and distribute data. Data is stored in memory to minimize response times for data requests
Finally found something that has ‘VMWare’ mentioned in it in respect to the SharePoint Distributed Cache.
Joerg Sinemus , Microsoft Germany states in his blog..
Caching services are used to improve performance because these services are optimized to work with the amount of memory installed on a server. In case the memory will vary during the uptime of the server, there might be a need to also implement those features into a Caching-Service. That makes no sense because of the nature a Caching Service has.
In other words our SharePoint product group cannot support scenarios when Distributed Cache is needed/running and someone has concerns about performance or stability because of Dynamic Memory configuration in any Virtual Environment.
The best way for a customer to make this guarantee is to set the VM sizes (static memory) of the guests such that their sum is less than the memory available on the physical machine, i.e. don’t use the overcommit feature or dynamic memory.”
Most of the environments I work in have Vmware for virtualisation, so I hope this clears up some doubts for VMware ESX Administrators until I get an official response from Microsoft.