Hello Eliot and welcome to the forum!
elwood wrote:Can anyone help give some steer on determining what is an acceptable number of IOPs for a VM to be generating?
It really depends on the capabilities and applications the VM is running. The problem can arise
if your virtual machines do not have enough I/O per second (IOPS) and IOPS available per virtual machine is less than 30.
elwood wrote:I'd like to know if there's an easy way in VeeamOne to assertain exactly how many IOPs the cluster / hosts / datastores are actually capable of.
This information should be given by your storage provider. Or use one of IOP calculators
You can also create a report with IOPs metrics for all or just group of VMs/datastores. In order to do that navigate to Workspace > New report > Templates > Custom reports > VMware Custom Performance
Or take a look at Top VMs IOPs in the relative dashboard