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Re: OT: Xen

  • From: Todd Vierling
  • Date: Mon Apr 03 09:26:53 2006

On Sat, 1 Apr 2006, David Lesher wrote:

> Panix is offering Xen-based virtual servers.  I mention same here
> only because I've seen almost no discussion of virtualized servers,
> and hope to learn from the surely-resulting flameware....

Xen and similar solutions are gaining popularity because they work on a
similar model as that used for ADSL:  most users don't use all the resources
all the time.  By virtualizing, the provider can offer "dedicated
colocation" at a somewhat lower cost to the user, and a *much* lower cost to
the provider.  If properly provisioned, by distributing more heavily loaded
virtual machines appropriately, you can probably attain virtualization of
20-30 or more per 2-way or 2-dual-core SMP box and still have CPU left over.

Note that Xen in particular has major advantages over some similar products
because it eliminates CPU-consuming system trap hackery needed to emulate
hardware devices and page-table mappings.  Xen is not, however, backed with
extensive commercial support (XenSource is still evolving at the moment),
lacks easy integration into popular UI/control-panel products, and requires
special kernels for the contained OS's (not such a big deal in practice).

The current problems haven't stopped some early adopters from trying out
Xen.  By and large, those who were once using UML[*] and have now tried Xen
have switched and not looked back.

[*] User Mode Linux, which I went out of my way to heckle (with technically
    sound arguments, mind you) at an IETF when it was proposed as a method
    of virtualization.  The sad part is, some folks bought the drivel and
    actually set up businesses using UML as a virtualization layer.

-- Todd Vierling <[email protected]> <[email protected]> <[email protected]>