[NTLUG:Discuss] Virtualization recomendations

[Bob Netherton]

On Fri, 2008-06-13 at 14:39 -0500, Fred Hensley wrote:
> For those interested in a critical evaluation of Xen, here are my thoughts:

Thanks Fred.  Good piece of fair and balanced - wish all the paid
analysts would be as thorough :-)   Full disclosure - I'm part of the
Xen adoption team at Sun - I will endeavor to be as fair and balanced.

>  and at nearly 
> bare-metal speeds with the Windows guests provided you take the quick 
> and simple additional step to load the Xen Windows drivers.

The PV drivers help quite a bit.   Once you introduce the
hyper-privileged level (root ring 0), the only penalty you pay
is for qemu emulated I/O and the PC drivers help a lot with this.
IOMMUs will be the next big step and the cost of virtualization
will be nearly zero.   The overhead for Intel's vmexit is going down
with each new spin of the processor.

> The free commercial version has been intentionally hobbled as follows:
> 1.  Maximum (4?) CPU's supported per server
> 2.  Maximum 4GB total server memory
> 3.  Maximum 4 concurrent guests running
> 4.  No ability to do live migration of running guests between Xen 
> servers, as the express version doesn't allow simultaneous server 
> management from the Xen console.

For a free product this doesn't seem to be too much of a limitation.  
The memory seems a touch small, especially for 4VMs, but I suppose they
know what they are doing.

> 1.  No support yet for software RAID. 

Is this in the domU or dom0 ?  We don't have that limitation at all.  In
fact we use ZFS in a lot of our prototypes without any difficulty -
except that ZFS likes memory - a lot :-)   So you limit the size of the
arc cache so it fits in the dom0 reserve and you are good.

> 2.  No PCI card support for guests.  

Yeah, the PCI passthrough was a cool feature of Xen 2 that we lost along
the way.  We aren't supporting it yet either, but it is on the list.

> 3.  The current management console for the commerical product is a .NET 
> application, and is not Mono compatible.  

This is where I depart company with our friends from Citrix.  There is
no reason to bring in Windows just for this use.    And just
because VMware does it is no excuse.  No reason you can't point a
browser at a dom0 configuration service written in java and transport
the console via one of the standard protocols.  RDP comes to mind for
the graphics consoles on Windows.  We don't need no stikin' graphics
consoles :-)

> 4.  Significantly less number of importable appliance (.xva) images.  
> There are a few, but nothing compared to the hundreds currently 
> available from VMware.

No kidding.  These things show up with the frequency of youtube videos.
I wonder what our friends from Redmond are going to say as they get
into the market.   IANAL, but I would think redistribution of the
Windows binaries is way in conflict with your EULA.



Appreciate the honest evaluation.  Thanks for sharing.


Bob