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There are a number of Xen based virtualization products on the market, and like with other new software, there is a need to try them out in a lab environment before doing production installation on customer sites.

I'm wondering if you could possibly run Oracle VM, XenServer or Virtual Iron inside VMware ESX, ESXi or VMware Server for testing purposes.

Or essentially, is there any way to avoid purchasing a new hardware cluster for each product?

update> I've now virtualized a complete Oracle VM environment within VMware without issues. Naturally all the guests are PVM. This makes is possible for me to gain experience with the Oracle VM platform without a hardware budget. Thanks everyone.

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up vote 3 down vote accepted

You can run Xen under VMware but you will only be able to run Linux guests (and other Xen-enabled guests).

Without hardware virtualisation support Xen provides only paravirtualisation which requires modified system software in the guests. Most Linux distributions come with Xen-compatible kernels.

The virtual machine created by VMware is a computer without hardware virtualisation support. I.e. VMware does not virtualise hardware virtualisation features.

So you can run Xen and run Linux guests within it.

But you cannot run Windows guests inside Xen.

(And yes, it's fast enough. The problem is just the missing hardware virtualisation.)

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I decided to give it a shot, and successfully virtualized a complete Oracle VM environment with manager, utility vm servers and an iscsi target server on VMware ESX 3.0. Two HA guests with OEL5 and Oracle 10g are running quite nicely. In short I'm getting valuable experience with Oracle VM without investing in any new hardware. – Roy Nov 8 '09 at 20:46
I haven't tried this yet, but I think you can run Windows guests as long as you create the template (and install the paravirtualization drivers) on a HVM capable machine. – Roy Nov 10 '09 at 18:27
The virtual machine created by VMware is a computer without hardware virtualisation support. – Andrew J. Brehm Nov 11 '09 at 9:17
Yes, this shortcomming have been metioned a few times. As for running PV enabled Windows guests, they unfortunately also require hardware support so it's pretty much RHEL and OEL only. – Roy Nov 13 '09 at 20:49

As the others note, lack of VT extensions are going to rule most hypervisors out. Not to mention overheads.

I have in the past used XenSource beneath another hypervisor (VMware mostly) for some specific staging tests. That works, but I wouldn't really recommend it.

Even if you do getting running you're likely to run into so many quirks that it doesn't justify itself as a reliable testbed. If hardware is a constraint you'd probably be better off dual booting.

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Hardware is always a constraint, especially when we're talking virtualization hardware and shared storage. In my particular case, all the lab hardware is already tied up in ESX and XenServer clusters. It's hard to justify additional hardware for Oracle VM. – Roy Nov 6 '09 at 11:43

I use cheap desktops for this testing these days; you can get >4GB memory and VT CPU's.

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+1 It's a good idea, but when you have added HBAs and rack mounting kits the price of a blade server might not be far off. Great if you can settle for iSCSI and put them on your desk. – Roy Nov 8 '09 at 20:55

The virtual CPUs presented by VMWare to each VM do not support hardware virtualisation.

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Not really, you can fiddle about with things and get Xen to boot inside VMware Workstation, but then starting guest OS's and so on is generally not going to work well at all.

It's much less hassle to buy a pair of very cheap HP ML110's or similar, but if you really want to do it, here's the instructions to install XenServer (which is very similar to both Oracle VM and Virtual Iron) on VMware workstation.

One thing to note is that Virtual Iron has already been discontinued after it's purchase by Oracle, instead the features from it will be included in Oracle VM's next versions.

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Even if you can trick it into working, you will not have a satisfactory experience.

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If you use only paravirtualized guests, Xen will work fine under VMWare. Paravirtualized guests don't need any special hardware support.

Its when you try to run unmodified guests that require hardware support under Xen (VT, AMD-V) that you'll get into trouble. The virtual processor given to Xen by VMWare will not have those extensions regardless of the underlying hardware.

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