I’m catching up with other blogs in the virtualization space. My fellow bloggers Chris Wolf and Mike D both have blogposts on the topic of DPM (Distributed Power Management)
In case you don’t know the concept is this: Coupled with some performance monitoring tools such as VMware DRS and some kind of live migrate feature like VMware VMotion. The system detects that you could actually move VMs around to then allow the power off of physical hosts into ACPI Standby mode. As the load peaks or returns, these physical hosts are then booted by using the “Magic Packet” associated with the Wake-On-LAN support on most NICs (a feature that's been around since the advent of PXE). The selling point is you consume less power when the VMs are not in use.
Currently this feature (like many in Vi3.5, grrr) is “experimental” i.e: not fully supported but should work. So from the get-go you're unlikely to get this approved for production use in corporate datacenter where “full support” is the only rule. So, the bigger question is what’s the point and is it worth while?
I would probably be conservative right now and agree with Chris Wolf’s take on this. BUT… there are cases where it could be quite compelling. Firstly, how about only powering on physical hosts in DR location when its needed, and based on how much you power on based on different recovery scenarios. Great idea huh? Well, yes – but for the moment such DR tools like VMware’s very own Site Recovery Manager are not supported in this configuration. Secondly, in non-mission critical environments such as test & dev it would be extremely wise to only power on what physical ESX hosts you need, when you need them. Thirdly, and this would be a bit more contentious is in VDI, only power on ESX hosts when users demand additional resources – or concurrency demands it.
As for production server based VMs providing network services to hundreds of users, it would take a brave man who would rely on a magic packet to power on an ESX host. For me in the world corporate datacenters – the only thing that powers on or off is a physical host that's human being authorized by change-management request….