Re: need help with PowerCli script to detach RDM devices not datastores

No, you can be connected to the vCenter.

Get all the ESXi in the cluster, and then call the function for each ESXi host.

Something like this

Get-Cluster-NameMyCluster|Get-VMHost|%{    Detach-Disk-VMHost$_-CanonicalName$canonicalname
}