On Friday, January 4, 2019 11:54 PM, Jim Mattson wrote: > On Fri, Jan 4, 2019 at 2:03 AM Wei Wang <wei.w.wang@xxxxxxxxx> wrote: > > > > On 01/03/2019 11:34 PM, Jim Mattson wrote: > > > Fast forward to, say, 2021. You're decommissioning all Broadwell > > > servers in your data center. You have to migrate the running VMs off > > > of those Broadwell systems onto newer hardware. But, with the > > > current implementation, the migration cannot happen. So, what do you > > > do? I suppose you just never enable the feature in the first place. Right? > > > > I'm not sure if that's the way people would do with their data centers. > > What would be the point of decommissioning all the BDW machines when > > there are important BDW VMs running? > > TCO increases as hardware ages, while the TCO for each successive > generation of hardware tends to be lower than its predecessor. Thus, the > point of decommissioning all BDW hosts that are beyond their useful service > life is to save money. Our assumption for Google Cloud is that we will always > be able to emulate older Intel processors on newer Intel processors, so the > running BDW VMs should not be affected by the decommissioning of BDW > hardware. Obviously, that means that we won't offer features that don't > have a forward migration story, such as this one. > > Yes, someday Intel will drop support for some feature that we currently offer > (like MPX, perhaps), and that will cause us some grief. This sounds like a pretty good opportunity to convince your customers to upgrade their VMs :) So the solution to your above problem I have in mind currently is: - expect QEMU's support to upgrade VMs (e.g. BDW to SKL) - just disable the non-compatible features for non-upgraded VMs (this could be in your SLA) Anyway, I think it would be good to get this feature online first, and then re-visit that future concern. Best, Wei
