[NTLUG:Discuss] Virtualization recomendations

Fri Jun 13 14:39:00 CDT 2008

For those interested in a critical evaluation of Xen, here are my thoughts:

The latest open source version (v3.2?) has all the options I need, but 
has had some issues for me regarding networking and some unexpected 
host/guest crashes.. Clearly ymmv...

For my critical clients who have a mix of Windows and **nix servers, I 
have taken full advantage of the "free" version of the Xensource 
commercial package called Xen Enterprise Express, currently version 4.  
Open source purists can understandably feel free to stop reading now..

The free version of their commercial package has been nearly bullet 
proof using the VT extensions described below by Chris, 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 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.

In addition, there are some further little problems with **any** of the 
commercial flavors I have been able to live with thus far:

1.  No support yet for software RAID.  While we are good-to-go with the 
open source version, they have kept things simple by only permitting 
fully hardware RAID cards to work which are completely transparent to 
Xen.  I have had great success using the 3Ware hardware RAID 
controllers, but they have a hardware compatibility list somewhere on 
the Xensource (aka Citrix) site.
2.  No PCI card support for guests.  Again, the open source can permit 
selected Guest OS access to various PCI cards, the commercial version 
has kept that feature out for now.  This was a problem for me when 
creating a surveillance system guest (Zoneminder) using a linux video 
capture card, and there are countless other examples where this might be 
a real problem, but they are (supposedly) working on enabling that feature.
3.  The current management console for the commerical product is a .NET 
application, and is not Mono compatible.  Therefore, I have to run the 
Xen server/guest management console from a Windows machine.  The last 
commercial release of Xen used a web client, and they are supposedly 
working on a new webclient version, but for now it is a pain.
4.  Significantly less number of importable appliance (.xva) images.  
There are a few, but nothing compared to the hundreds currently 
available from VMware.

The three big positives, for me, remains the simplicity of server/guest 
installation, easy console management (from a Windoze machine or guest), 
and fast-fast-fast performance for the Windows guests.  Perhaps the 
VMWare ESX version has similar performance benchmarks for Windows 
guests, but I haven't yet had the opportunity to explore.  As with all 
commercial offerings, Xen (or VMWare) are free to change the rules for 
their products whenever they choose..

Lastly, I recently worked the guys at Openfiler 
(http://www.openfiler.com) and Xensource (http://www.xensource.com) to 
beg/borrow/plead an xva importable Openfiler image, and (Openfiler, 
Rpath, and Xensource) worked together to create an xva appliance image 
which really helped me...

My $0.02,

-Fred-

So,
Chris Cox wrote:
> Ted Gould wrote:
>   
>> On Fri, 2008-06-13 at 10:24 -0500, Bob Netherton wrote:
>>     
>>>> Oddly enough, Ubuntu has decided to standardize on KVM instead of Xen. 
>>>>
>>>> http://news.cnet.com/8301-13580_3-9867657-39.html
>>>>
>>>> I have privately wondered whether it had anything to do with the Citrix 
>>>> acquisition of Xen, or some new Citrix strategies afterwards.
>>>>         
>>> I had seen that.  I don't run into that many customers running Ubuntu -
>>> sure lots of folks running it at home (I do, but more in a keeping up
>>> with the Joneses voyeurism).  I attribute the decision more to the
>>> Ubuntu approach of keeping close to the core bits (kernel + GNOME) and
>>> use derivative distributions for projects that don't align conveniently
>>> to the release schedule.  Maybe there's more to it than that, but the
>>> Xen release schedule would make me lose what's left of my hair if I had
>>> to build product plans around it :-)
>>>
>>> I know Thomas Cameron is around here - but being suspiciously quiet :-)
>>>       
>> I have heard that privately Redhat's position is:
>>
>>         We have enterprise customers who we support using Xen.
>>         Therefore we support Xen.
>>         
>> But internally they see KVM as the future.  (thus the investment into
>> virtualization manager and others)  The fact that Xen requires modified
>> guests and has a significant number of Kernel patches that are required
>> makes it a hard sell for any distribution.  Especially those starting
>> with a clean slate.
>>     
>
> Early Xen was only paravirtualized guests... but with the VT extensions
> made by Intel and AMD, full virtualized guests are possible (e.g. Windows).
>
> Paravirtualization gets you the performance gains.... Novell's work
> with Microsoft (love it or hate it) has helped to produce the
> paravirtualized drivers necessary for Windows guests.  So Xen not
> only can support full virtualized (unmodified) Windows guests, but
> can now also support a level of paravirtualized acceleration.
>
> Does KVM do windows guests now?  I know it didn't at first.
>
> We'll all have to see if Xen overtakes VMware or if something
> else does.  I know we're looking at Xen as a possible replacement
> for VMware now.
>
>
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