Virtual Insanity...

[jsbowden]

Okay, so I've been playing with virtualization over the last few weeks (VMware, Virtual PC, and XEN), and I'm kind of not seeing the point.

Okay, loading up Virtual PC on my machine at home, and installing Win98 so I can play old games is nifty and all (and hey, my motherboard even has hardware support for VMs, which Vitual PC can and does take advantage of...), but the whole server virtualization thing eludes me.

I mean, how is running a bunch of VMs is any less resource intensive than running a bunch of jailed processes (or, chrooted if you're still living in the dark ages :P)? In fact, as far as I can tell, it's MORE resource intensive, since I have to dedicate hard amounts of memory to each VM, where jails just use memory as needed out of the system total. I'm going to be running the same services either way, I don't see less processor cycles used, it's more, actually since that VM's local OS has its own overhead it has to take care of.

Am I missing something here? This looks like a solution looking for a problem. I can see where it could be useful in the same way building a bootable CD/DVD to run an OS off of is useful, except less secure since the VMs disk image can be fucked with, unlike immutable optical media.

EDIT:

So, after chatting with some friends, it seems VMs make things like patching and DR easier, which I can see, and it abstracts HA out to an easier to manage level, which is nice. Still, not going to save the planet moving everything to VMs, and some things still belong on dedicated hardware (which, may mean a single host/guest arrangement if you're hardcore on doing VM everywhere, no matter what).

Comments

[jsbowden.livejournal.com]

Well, see, this is where I live in a Unix centric mindset still.

If my services have different peak times, that makes them perfect for sharing space on the same server, each with it's own chroot/jail containing what it needs, and only what it needs, to run and run well.

This is, apparently, not something easily done, if it can be done, in Windows land (for me, our Windows servers exist to serve Windows AD and associated bits to Windows clients, not be internet facing providers of critical services).

I'm well aware of using VMs for developement and test environments, I'm just not seeing the use for production servers, but mostly that's me living in a mindset where I can isolate processes individually without needing to throw a whole (virtual) machine, and the associated resources required, at them to do so.

[corruptedjasper.livejournal.com]

It's not that easy in linux, either. A virtualisation environment abstracts all that out, so you can just copy a clean installed disk image over and have your secondary (heptadecary) separate environment.

And if a particular service used to be 10-12 usage and is now 10-16 usage and conflicting with another service, why, then you move the virtual disk image file to a different set of hardware and boot it up again. That flexibility is something that no chroot jail will ever have.