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Re: [libvirt-users] Can a VM tell what host it's on?



On Thu, Feb 02, 2012 at 02:30:45PM -0500, Brian K. White wrote:

> I certainly don't have any such thing as a central management app
> that knows what all the vm's are on all the hosts.

At the level of the VM, I'd certainly hope going forward that there's no
assumption of a "central management app" at all. The beauty of a UNIX
component-tool architecture is that the parts can be recombined in novel
ways for very different projects. A VM is going to be a more
generally-useful part if it has access to contextual information re: where
it's running. And there are going to be more ways to assemble the local
architecture around the VM if the tools both outside and potentially inside
the VM make no assumptions about being in a context where a "central
management app" exists at all. They shouldn't depend on that assumption.

The whole Internet is arguably based on an ideal of distributed management
rather than central management. Capitalism is too, for that matter. While
it's quite understandable that a particular Linux distro will want to
feature a polished, one-size-fits-all cluster stack - and it's wonderful
that the market for such a solution can fund and encourage the development
of the underlying pieces - in the *nix world it should be expected and even
encouraged that those pieces will be refitted into contexts of quite
different design.

As such, the components should have flags and hooks available to them which
are not part of the spec of the one-size-fits-all cluster stack, to
facilitate their reuse in novel contexts. Sure, a lot of that reuse will be
rinky-dink stuff of poor design. But some of it will blossum into stuff that
can feed back into improving the models used by the main-stream distros. 

Gluster is a good example, in a way. It was created by people who weren't
"real" file system engineers, so hadn't received the conventional wisdom on
the "right" way to do it. They did it "wrong." Yet RH just paid big bucks
for it, warts and all, because it turns out to be smarter than the file
system end of the current RH cluster stack, at least in potential. And RH's
said some very positive stuff about making sure that Gluster's even more
open to diverse use and development than it was under its old owner.

That seems like the right philosophy for all this stuff.

Best,
Whit


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