One of the recent features of the vSphere Cluster Services (vCLS) is the ability configure the vSphere Datastores that vCLS is allowed to use to provision the required service VMs, which can be on a vSphere Cluster under Configure->vSphere Cluster Services->Datastores as shown in the screenshot below.
In addition to the vSphere UI, you can also programmatically update this configuration using the vSphere API and with tools like PowerCLI as one of the interfaces to the API.
In vSphere 7.0 Update 1, a new capability was introduced called the vCenter Cluster Services (vCLS) which provides a new framework for decoupling and managing distributing control plane services for vSphere. To learn more, I highly recommend the detailed blog post linked above by Niels. In addition, Duncan also has a great blog post about common question/answers and considerations for vCLS, which is definitely worth a read as well.
vSphere DRS is one of the vSphere features which relies on this new vCLS service and this is made possible by the vCLS VMs which are deployed automatically when it detects there are ESXi hosts within a vSphere Cluster (regardless if vSphere DRS is enabled or not). For customers who may be using the ESXi-Arm Fling with a vSphere 7.0 Update 1 environment, you may have noticed continuous "Delete File" tasks within vCenter that seems to loop forever.
This occurs because the vCLS service will first test to see if it can upload a file to the datastore, once it can, it will delete it. The issue is that the vCLS VMs are x86 and can not be deployed to an ESXi-Arm Cluster as the CPU architecture is not supported. There is a workaround to disable vCLS for the ESXi-Arm Cluster, which I will go into shortly. However, because vCLS can not properly deploy, it means vSphere DRS capabilities will not be possible when using vSphere 7.0 Update 1 with ESXi-Arm hosts. If this is desirable, it is recommended that to use either vSphere 7.0c or vSphere 7.0d if you wish to use vSphere DRS.
Note: vSAN does not rely on vCLS to function but to be able to use it, you must place your ESXi-Arm hosts into a vSphere Cluster and hence applying this workaround would be desirable for that use case.