[clug] Idle thought: can I migrate processes from a high-power to a low-power system?

B boydwilding at gmail.com
Wed Mar 6 02:39:20 MST 2013


I feel confident saying that migrating a running VM across architectures 
in the way that you're describing, is difficult at best. Not necessarily 
impossible, but very hard to achieve without a lot of wheel 
re-inventing! (or just plain inventing!).

I think it is an awesome idea, and I would be very interested in seeing 
an example of this magic working in front of me, but haven't heard of 
such a thing without a large amount of hardware commonality being present.

 From my experience with vmware, there are ways to dumb-down CPU 
features (in VMWare-speak, called EVC, enhanced vmotion capability), so 
that you can migrate a VM from one host with CPU stepping X to another 
host with CPU stepping Y, without a problem, but you need to be using 
the same CPU vendor and definitely the same architecture, (plus the 
aforementioned shared storage) to make it all possible.

On 06/03/13 16:52, steve jenkin wrote:
> Last night I started downloading the latest Debian ISO images in
> preparation for an install on a new Desktop PC.
> As I left 'wget' running, I thought "geez, I'd like to be able to put my
> PC to sleep and move this transfer to something low-power, like a
> Raspberry Pi."
> If I was running the right sort of VM system, I could migrate any
> running VM from one Intel processor to another compatible processor.
> That assumes the target long-running process is the only one running in
> that VM.
> And that there is a common filestore shared by the hypervisor on both
> host systems, or there's a fast migration possible of open files from
> local storage on one to another. [I had 4.4GB ISO's]
> The obvious "drop-dead" was the two different architectures, x86 and
> ARM. 'emu' does emulate multiple architectures, I'm not sure how well.
> So in my scenario, if I'd started my wget in a VM under 'emu' emulating
> ARM on x86, I may have been able to migrate the task+VM to a Raspberry
> PI, if I had one [and it supported VM's & migration].
> The other solution is to migrate VM's from like-to-like architecture,
> but the usual problem is that low-power x86 (eg Atom) don't have the
> higher-level VT-x instructions often required by hypervisors...
> My question:
>   - Does anyone (routinely) *do* live-migration of long-running tasks,
> especially from hi-spec to low-spec x86 architectures?
>   - Across different architectures?
>   - OR, has anyone seen a paper or something being developed that leads
> in this direction?
> It'll be 6 months or more before I get to look at this question for
> real. Had the thought and wanted to get any feedback so I can start
> researching it over the next few months.
> There may be something simple I can do in my initial setup that will
> provide this pathway. If so, now is the best time for me to do that.
> Thanks in advance.
> steve
> PS: I bought a 250Gb Samsung 840 SSD [not the Pro] today from MSY @
> Fyshwick.
> They redefine the concept of 'customer service', but gotta love their
> prices.
> Thanks for all the feedback/suggestions/input on- and off-list.

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