Homelab: Downsizing vCenter Server Appliance 6.5

In vSphere 6.5 the smallest supported memory configuration for the vCenter Server Appliance has been raised from 8GB to 10GB. The smallest "Tiny" deployment size allows up to 10 ESXi Hosts and 100 Virtual Machines. Resources in Homelabs are limited and you might want to lower the memory consumption of the vCenter Servcer Appliance. This article explains how to lower the resource consumption to be able to lower the memory to about 6GB without noticable impacts.

Please note that the smallest supported vCSA size is 2 vCPU and 10GB Memory. Any further downsizing is not supported by VMware. Don't do this in production.

Some vCenter Server Appliance Basics

The vCenter Server Appliance (vCSA) comes with a neat dynamic memory allocation functionality, that automatically adjusts the memory configuration based on the configured total memory. The allocation can be viewed with the cloudvm-ram-size command. The following output is from a "tiny" vCenter with 10GB memory:

# cloudvm-ram-size  -l
vmcad                =      224
vmafdd               =       22
vmware-rbd-watchdog  =      100
applmgmt             =      200
vmware-vsan-health   =      100
vmware-vsm           =      160
vmware-sps           =      478
vmware-stsd          =      538
vmware-vpostgres     =      699
vmware-psc-client    =      288
vmware-eam           =      168
vmware-sts-idmd      =      328
vmware-mbcs          =      128
vcha                 =       46
vmware-vmon          =        5
vmware-statsmonitor  =       10
vmware-perfcharts    =      357
vsphere-client       =      853
vmonapi              =       15
vmware-cm            =      228
vmware-rhttpproxy    =       31
vmdird               =       22
vmware-imagebuilder  =       50
vmware-sca           =      128
vmware-vpxd          =     1024
vsphere-ui           =      853
vmware-vapi-endpoint =      256
vmware-content-library =    473
vmdnsd               =       20
vmware-cis-license   =      192
vmware-updatemgr     =      164
vmware-vpxd-svcs     =     1045
OS                   =      775
vmware-netdumper     =       20
TOTAL(MB)            =    10000

After increasing or reducing the virtual machine memory, each service is adjusted automatically but they will never go below 10000MB. If you want to know how far each service can grow, take a look at the configuration file at /etc/vmware/service-layout.mfx.

Dispensable Services

Prior to actually lower the memory you should consider disabling services. Disabling services is always a tradeoff between functionality and resources requirements. The following services are not running by default and are already lowering the resource consumption by 294MB.

Another few services can be disabled without major impact to the vCenter:

VMware vSAN Health Service
If vSAN is not in use in the infrastructure managed by the vCenter Server it is safe to disable the vSAN Health Service. Disabling the vSAN Health Service is also explained in VMware KB2145308. 

VMware vSphere Profile-Driven Storage Service
This service is required when using Virtual SAN, Virtual Volumes or any other policy-driven Storage scenarios.
[Update: Stopping this service leads to problems when creating or migration Virtual Machines.]

• A general system error occurred:  PBM error occurred during QueryAllAssociatedProfiles: Connection refused
• A general system error occurred: PBM error occurred during PreMigrateCheckCallback: No connection could be made because the target machine actively refused it.

VMware Performance Charts
In the vSphere Web Client you can view pre-rendered performance graphs for supported objects within Performance > Overview. Disabling this services removes this feature and an error message is displayed when you open the Performance Overview Tab. The graphs in the Advanced view are not affected, they still work.

VMware Content Library Service
Removes the Content Library functionality. After disabling this services you also see a warning for the vAPI Endpoint. However, I have not noticed any further problems.

VMware Update Manager
Since vSphere 6.5 the Update Manager is included in the vCenter Server Appliance, which is great. If you don't need it, you can disable the Service. Update Manager related tabs will remain in the Client but when you open it you see an error message.

VMware vSphere Client (HTML5)
The HTML5 based Webclient is a new feature in vSphere 6.5 and will probably replace the Flash-based client in future releases. If you don't want to use it, it is safe to disable.

Disable Services

To disable a service, open the vSphere Web Client and navigate to Administration > Deployment > System Configuration > Services. From here you can stop services and configure the Startup Type to manual which will prevent services from starting automatically.

Stop a running service

 Disable service autostart

How far can I lower the vCSA Memory?

When you've disabled all services mentioned in this article you should be able to reduce the memory by about 2.2GB:

How much you can actually lower your vCSA memory depends on your Homelab size and your performance requirements. I've downsized my vCenter managing 4 ESXi Hosts to 6GB and haven't noticed any issues. Sure you can lower it further, but at 5 GB I started to notice a performance impact.

Can I disable additional Services?

In this article, I've mentioned services that are kind of safe to disable. It might be possible to disable more services but I wouldn't recommend so. If you want to explore further, here is a list of all services with their memory allocation. Be careful when disabling services from starting with the appliance when you don't know the impact as this can prevent the vCenter from starting.