Re: [Xen-users] IBM x445, anyone using it?

["Jeff Lane" <sundowner225@xxxxxxxxx>]

On Mon, May 19, 2008 at 2:15 PM, isplist@xxxxxxxxxxxx
<isplist@xxxxxxxxxxxx> wrote:
> What type of processors should I be looking for which are properly supported 
> then?

If you want to run full virtualization, any of the newer dual/quad
core Intel and AMD chips support virtualization.  For intel, this
should include the latest Xeons, Core 2 chips and others.. not sure
about Celerons though.  For AMD, the newer AMD64 chips do, both dual
and quad core, and maybe some of the newest single core chips too, but
I am not positive on actual model names/numbers...  at least, I don't
have a list of names/models handy.

> It's just a fresh CentOS install with Virtualization because I wanted to try 
> out Xen.

Like I said, you have Domain 0 running, so Xen is doing its thing...
dom0 is just a paravirtualized guest to begin with.

> I'm not sure that there is a problem, perhaps a little configuration which is 
> not installed by default or such?

Maybe...  I've never used CentOS, but I've done hundreds of RHEL Xen
installs and have yet to run into issues like what you're seeing, and
since CentOS is mostly rebadged RHEL, the differences should be
minimal between the two...

>> Really, use virt-manager or YaST and install a paravirtualized guest
>> just to see if it works.  Besides, you have a running system, and a
>> running Dom0, so Xen works.  Dom0 is, in reality, just a
>> paravirtualized guest OS running on the hypervisor.
>
> That's exactly what I've tried and received the path error :).
> Using Virtual Machine Manager, I've tried to install a pre-configured ISO. It 
> was simply what I had handy. I can try something else. Is there
> something I can try from the command line? I just want a basic Linux install, 
> no servers, nothing for now.

I think that may be the key there... you're using a preconfigured ISO?
 I assume this means a preinstalled Guest image?  To be honest, I've
tried several flavors of those and never gotten one to boot.

What I was suggesting, and for paravirt you'll have to do it this way:
 build an NFS mountable (or http mountable) install tree using the
CentOS install media, NOT the preconfigured thing you're using now.

Then use Virt-manager to create a new guest from scratch.  Tell it you
need to install an OS (YaST asks this, can't remember of virt-manager
does or not) and for installation source, use the nfs or http URL for
your install tree.

For example.... I have two servers.  S1 is a NFS/HTTP server that
hosts installation trees built from DVDs (I just copy the DVD contents
from INSTALLATION DVDs into a directory like /install/distro-name.  S2
is a Xen host that I want to install a guest on.

So, on S2, launch virt-manager.  Connect to the hypervisor and click NEW.

Give the guest a name.
Choose Paravirtualized (that should be your only option on this box)
On the Install media line on the next screen, enter
http://ip.of.server./path/to/installtion/tree
  In my case, the install media line looks like this:
http://172.0.0.253/install/RHEL5.2/  which points to a full install
tree for RHEL 5.2.
Select simple file on next screen and make it at least 6 - 8 GB (I've
found that the 4GB default is not usually big enough once you add in
swap)
Be sure the "Allocate entire virtual disk now" option is checked.  I'm
not a fan of sparse files...  better IMO to have the full filesystem
allocated than not have room later...
Choose your network settings as appropriate for your environment
Choose memor and VCPUs as appropriate.  Also note, I normally make
guests with a minimum of 1024M RAM...  but I have memory to spare.

Now, provided that your install tree is created correctly and is
network accessible, you should be ready to go.  Clicking finish on the
last screen will start the guest and being the install process.

You can also put a file tree on your local machine...  If you do that,
though, I think you may still have to have nfs or apache running to
make it available, because what you are basically doing is a network
install of the OS onto the new guest.

> It's an ISO of a pre-installed CentOS OS with qmail pre-configured along with 
> other tools. Just had it handy when I first gave this a quick try.

Thanks for pointing that out.  I was confused.  See above.  Like I
said, I've never really had much luck with preconfigured Xen guests.
I HAVE run preconfigured guests in VMWare before, but the Xen ones
always seem to fail for one reason or another... but I don't remember
ever seeing the error you were seeing, but now that I understand what
you are trying to do, let me correct that to say that I dont remember
seeing it, meaning  I may well have seen it and just didn't recall...

> That's fine, like I too said, I just happen to have these machines sitting 
> here so was hoping I might be able to use them with Xen. From what I can
> tell, I won't be needing fully virtualized machines anyhow. I don't tend to 
> consolidate things which I try to get the most power from. In other words,
> I won't be virtualizing machines which need to be as powerful as they can be. 
> I will be virtualizing machines which don't do a lot, DNS servers for
> example are pretty simple I/O machines, very low use web, mail, other 
> servers, things like that.

Honestly, I do all this in a test environment... I beta test Linux for
a living, so I dont get the chance to use this stuff in the "real
world" like a lot of you do.  The upside is that I have done this a
LOT, the downside, is that my installations never live longer than a
week before they are flattened and rebuilt.

That being said, for what you want to do, If at all possible, I would
move to a 64bit machine and run 64bit Xen, using 64bit and 32 bit
guests.  Using a 32bit Xen machine limits you to the 32bit memory
limits and prevents a lot of expansion.  64bit systesm let you use a
LOT more ram and gives you the benefit of being able to run both 64
and 32 bit guests on your host system.

Also, I wouldn't worry too much about hardware virtualization unless
you discover a REAL need for it (like running unmodified Windows
guests, etc) because HVM guests tend to be a lot slower than paravirt
guests, in my experience.  (and for you Xen gurus out there, no, I
don't do any real bench marking... this is more of a seat of the pants
kind of experience...)

Hope that helps...

Jeff

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