Wes, Unfortunately, we're very far from this. There are three different types of hypervisor: software (VMware), hardware (Xen, et al), and paravirtualized (VMware + VMI, Xen in paravirt mode, etc.). Despite the fact that folks claim that unmodified VMs can run under Xen, in the real world *everyone* provides customized network and disk drivers for the guest OS because the performance is abysmal. These are 'paravirtualized drivers', which is why the performance can be so dramatically affected. Unfortunately, there isn't a standard of any kind, so you'll find that the paravirt drivers for disk drives for the SLES Xen hypervisor will have problems running under the RHEL Xen hypervisor and vice versa. The same kind of issue holds true for VMware where you just won't see acceptable performance unless the VMware drivers and tools are installed. Now, you could say: "Well, folks will just have a performance hit" and I would agree if we were talking about inside the firewall, but the reality is that in public clouds folks are very eager to get the maximum performance from a single instance in order to maximize their dollars spent. So you are quickly in a situation where ignoring the OS isn't feasible. Even though OVF doesn't provide for this, it SHOULD. It's an oversight on the part of VMware and Xen. Once providers start allowing uploading of arbitrary VM images, they are also going to need what OS is in the image package so that they can dynamically install the correct paravirt drivers for the hypervisor they are using. If you don't have this capability then allowing the upload of completely opaque images and hoping they will have any kind of reasonable performance on an arbitrary cloud providers system is a pipe dream. This is an area badly in need of standardization, but I doubt it will come any time soon. --Randy On Jun 14, 2009, at 1:44 PM, Wes Felter wrote:
On Jun 14, 2009, at 6:35 AM, Gary Mazz wrote:
Sam Johnston's timely IaaS feature matrix brings up some interesting issues, one in particular, what are the specific features that can be included in an IaaS.
Many of the IaaS provider are also providing one or more operating systems while other are providing closer to bare metal. Is the OS part of the Infrastructure or part of the Platform ?
IMO IaaS is about flexibility and thus should provide bare metal (or virtual bare metal) so that customers can use any OS they choose. OVF seems to require this, since an OVF image can contain any OS; thus if your IaaS claims to support OVF then you should be able to run *any* OVF image containing *any* OS. I think this also requires full virtualization since paravirtualization is neither standardized nor widespread.
IaaS providers can provide optional prebuilt OS images, but it shouldn't be part of the infrastructure.
Wes Felter - wesley@felter.org - http://felter.org/wesley/
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Randy Bias, Cloud Strategist +1 (415) 939-8507 [m], randyb@neotactics.com BLOG: http://cloudscaling.com